TMEM41B Is a Pan-flavivirus Host Factor Hoffmann, H.-Heinrich; Schneider, William M.; Rozen-Gagnon, Kathryn ...
Cell,
01/2021, Volume:
184, Issue:
1
Journal Article
Peer reviewed
Open access
Flaviviruses pose a constant threat to human health. These RNA viruses are transmitted by the bite of infected mosquitoes and ticks and regularly cause outbreaks. To identify host factors required ...for flavivirus infection, we performed full-genome loss of function CRISPR-Cas9 screens. Based on these results, we focused our efforts on characterizing the roles that TMEM41B and VMP1 play in the virus replication cycle. Our mechanistic studies on TMEM41B revealed that all members of the Flaviviridae family that we tested require TMEM41B. We tested 12 additional virus families and found that SARS-CoV-2 of the Coronaviridae also required TMEM41B for infection. Remarkably, single nucleotide polymorphisms present at nearly 20% in East Asian populations reduce flavivirus infection. Based on our mechanistic studies, we propose that TMEM41B is recruited to flavivirus RNA replication complexes to facilitate membrane curvature, which creates a protected environment for viral genome replication.
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•TMEM41B is required for flavivirus infection, but autophagy is not required•TMEM41B associates with flavivirus proteins and may facilitate cell membrane remodeling•TMEM41B single nucleotide polymorphisms reduce flavivirus infection•TMEM41B-deficiency confers a heightened innate immune response to flavivirus infection
Hoffmann et al. determine that the transmembrane protein, TMEM41B, is required for infection by members of the Flaviviridae family of viruses. Loss of TMEM41B reduces viral RNA replication and increases innate immune activation in response to flavivirus infection. Thus, TMEM41B is a potential host target for antiviral therapeutics.
To investigate the movement characteristics of cylindrical particles within a slurry pump, the particle trajectories, particle distributions, particle velocity, and passing time of particles in the ...guide vane are tested by high speed photography. The test results indicate that the pump performance decreases and the wear of the blade pressure side deteriorates with the increase of cylindrical particle densities. The particles primarily flow into the guide vanes from the suction side and flow out from the pressure side. The velocity loss of particles in the guide vanes increases, and the time for particles passing through the guide vanes increases with particle densities. As the cylindrical particle concentrations increase, the pump performance decreases, and the wear of the blade pressure side deteriorates. Additionally, the total velocity loss of particles in the guide vane increases, and the time for particles passing through the guide vane increases with concentrations. Compared with spherical particles, the pump performance is better when the pump conveys cylindrical particles, and the cylindrical particles are more likely to wear the middle of the guide vane flow channel. The particles mainly flow into the guide vanes from the suction side and flow out from the pressure side. The velocity loss of cylindrical particles in the guide vane is smaller than that of the spherical particles. The time of cylindrical particles passing through the guide vane is shorter than that of the spherical particles.
Antiviral resistance of stem cells Wu, Xianfang; Kwong, Andrew C; Rice, Charles M
Current opinion in immunology,
02/2019, Volume:
56
Journal Article
Peer reviewed
Open access
•Stem cells are resistant to infection by diverse viruses.•Stem cells and differentiated cells use distinct antiviral resistance mechanisms.•Interferon responsiveness may be incompatible with stem ...cell function.•Intrinsic interferon-stimulated gene expression may be vital to stem cell identity.
Stem cells are important for growth and regeneration given their ability to self-renew and differentiate into mature cells. Resistance to certain viral infections has been established as a phenotype of stem cells, a protection in line with their important physiological function. Antiviral resistance is critical to all cells, but it is differentially regulated between stem cells and differentiated cells. Stem cells utilize antiviral RNA interference, interferon-independent repression of endogenous retroviruses and intrinsic expression of antiviral interferon-stimulated genes. Differentiated cells often rely on the interferon-associated protein-based response to induce a local antiviral state. This review outlines the antiviral resistance mechanisms of stem cells and discusses some ideas as to why stem cells and differentiated cells may have evolved to utilize distinct mechanisms.
A number of genetic polymorphisms have been associated with susceptibility to or protection against non-alcoholic fatty liver disease (NAFLD), but the underlying mechanisms remain unknown. Here, we ...focused on the rs738409 C>G single nucleotide polymorphism (SNP), which produces the I148M variant of patatin-like phospholipase domain-containing protein 3 (PNPLA3) and is strongly associated with NAFLD.
To enable mechanistic dissection, we developed a human pluripotent stem cell (hPSC)-derived multicellular liver culture by incorporating hPSC-derived hepatocytes, hepatic stellate cells, and macrophages. We first applied this liver culture to model NAFLD by utilising a lipotoxic milieu reflecting the circulating levels of disease risk factors in affected individuals. We then created an isogenic pair of liver cultures differing only at rs738049 and compared NAFLD phenotype development.
Our hPSC-derived liver culture recapitulated many key characteristics of NAFLD development and progression including lipid accumulation and oxidative stress, inflammatory response, and stellate cell activation. Under the lipotoxic conditions, the I148M variant caused the enhanced development of NAFLD phenotypes. These differences were associated with elevated IL-6/signal transducer and activator of transcription 3 (STAT3) activity in liver cultures, consistent with transcriptomic data of liver biopsies from individuals carrying the rs738409 SNP. Dampening IL-6/STAT3 activity alleviated the I148M-mediated susceptibility to NAFLD, whereas boosting it in wild-type liver cultures enhanced NAFLD development. Finally, we attributed this elevated IL-6/STAT3 activity in liver cultures carrying the rs738409 SNP to increased NF-κB activity.
Our study thus reveals a potential causal link between elevated IL-6/STAT3 activity and 148M-mediated susceptibility to NAFLD.
An increasing number of genetic variants manifest in non-alcoholic fatty liver disease (NAFLD) development and progression; however, the underlying mechanisms remain elusive. To study these variants in human-relevant systems, we developed an induced pluripotent stem cell-derived multicellular liver culture and focused on a common genetic variant (i.e. rs738409 in PNPLA3). Our findings not only provide mechanistic insight, but also a potential therapeutic strategy for NAFLD driven by this genetic variant in PNPLA3. Our liver culture is therefore a useful platform for exploring genetic variants in NAFLD development.
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•A hPSC-derived multicellular liver culture mimicking liver composition was developed.•Multicellular liver culture recapitulates many key features of NAFLD development.•Multicellular liver cultures harbouring PNPLA3I148M enhance susceptibility to NAFLD.•Elevating IL-6/STAT3 signalling promotes PNPLA3I148M-induced NAFLD progression.•Blocking trans-signalling by sgp130Fc protects against PNPLA3I148M-induced NAFLD progression.
Inherited genetic variations in the melanocortin-1 receptor (MC1R) responsible for human red hair color (RHC) variants are associated with impaired DNA damage repair and increased melanoma risk. MC1R ...signaling is critically dependent on palmitoylation, primarily mediated by the protein acyltransferase zinc finger DHHC-type palmitoyltransferase 13 (ZDHHC13). A better understanding of how ZDHHC13 is physiologically activated could help identify approaches to prevent melanomagenesis in redheads. Here, we report that AMP-activated protein kinase (AMPK) phosphorylates ZDHHC13 at S208 to strengthen the interaction between ZDHHC13 and MC1R-RHC, leading to enhanced MC1R palmitoylation in redheads. Consequently, phosphorylation of ZDHHC13 by AMPK increased MC1R-RHC downstream signaling. AMPK activation and MC1R palmitoylation repressed UVB-induced transformation of human melanocytes in vitro and delayed melanomagenesis in vivo in C57BL/6J-MC1R-RHC mice. The importance of AMPK to MC1R signaling was validated in human melanomas where AMPK upregulation correlated with expression of factors downstream from MC1R signaling and with prolonged patient survival. These findings suggest AMPK activation as a promising strategy to reduce melanoma risk, especially for individuals with red hair.
Phosphorylation of ZDHHC13 by AMPK at S208 promotes MC1R activation and suppresses melanocyte transformation, indicating activation of AMPK as a potential approach to prevent melanoma in people with red hair.
Human-induced pluripotent stem cell-derived hepatocyte-like cells (iHeps) constitute a powerful tool for modeling hepatotropic pathogen infections in cell culture. Meanwhile, CRISPR-Cas9 technology ...enables precise editing of stem cell genomes to generate patient-specific disease models and thus development of personalized experimental systems. Here we present a detailed stepwise protocol for the differentiation of stem cells to hepatocyte-like cells for HCV studies in cell culture. We also outline the use of an inducible iCRISPR platform for the rapid and efficient modification of host factors of interest to better understand their function during HCV infection.
Given the unprecedented scale of the recent Ebola and Zika viral epidemics, it is crucial to understand the biology of host factors with broad antiviral action in order to develop novel therapeutic ...approaches. Here, we look into one such factor: zinc finger antiviral protein (ZAP) inhibits a variety of RNA and DNA viruses. Alternative splicing results in two isoforms that differ at their C termini: ZAPL (long) encodes a poly(ADP-ribose) polymerase (PARP)-like domain that is missing in ZAPS (short). Previously, it has been shown that ZAPL is more antiviral than ZAPS, while the latter is more induced by interferon (IFN). In this study, we discovered and confirmed the expression of two additional splice variants of human ZAP: ZAPXL (extralong) and ZAPM (medium). We also found two haplotypes of human ZAP. Since ZAPL and ZAPS have differential activities, we hypothesize that all four ZAP isoforms have evolved to mediate distinct antiviral and/or cellular functions. By taking a gene-knockout-and-reconstitution approach, we have characterized the antiviral, translational inhibition, and IFN activation activities of individual ZAP isoforms. Our work demonstrates that ZAPL and ZAPXL are more active against alphaviruses and hepatitis B virus (HBV) than ZAPS and ZAPM and elucidates the effects of splice variants on the action of a broad-spectrum antiviral factor.
ZAP is an IFN-induced host factor that can inhibit a wide range of viruses, and there is great interest in fully characterizing its antiviral mechanism. This is the first study that defines the antiviral capacities of individual ZAP isoforms in the absence of endogenous ZAP expression and, hence, cross talk with other isoforms. Our data demonstrate that ZAP is expressed as four different forms: ZAPS, ZAPM, ZAPL, and ZAPXL. The longer ZAP isoforms better inhibit alphaviruses and HBV, while all isoforms equally inhibit Ebola virus transcription and replication. In addition, there is no difference in the abilities of ZAP isoforms to enhance the induction of type I IFN expression. Our results show that the full spectrum of ZAP activities can change depending on the virus target and the relative levels of basal expression and induction by IFN or infection.
PurposeThe purpose of the paper is to disclose the effect of the relative position (d) between the impeller and non-vane cavity on the hydraulic performance and unsteady characteristics of vortex ...pump.Design/methodology/approachThree groups of vortex pump models with different impeller installation positions were analyzed and studied by combining experimental and CFD (Computational Fluid Dynamics) numerical calculations.FindingsThe steady numerical results show that as the width (d) of the impeller moves into the non-vane cavity increases, the proportion of circulation flow in the non-vane cavity is reduced and both the pump head and efficiency are on the rise. The unsteady numerical results and the Enstrophy analysis show that the dynamic and static interference between the circulation flow and the volute tongue is the main reason for the pressure pulsation with a frequency of 2fn in the vortex pump. With the increase of the d value, the dynamic and static interference between the circulation flow and the volute tongue is enhanced. The pulsation amplitude at the volute tongue of the d = 16.5 mm model increases about six times compared with the d = 0 mm model; the distribution of the vortex core in the non-vane cavity is closely related to the position of the impeller, and the peak of the Enstrophy of the circulation flow vortex belt always appears at the top of the impeller.Originality/valueThe research results provide a theoretical foundation for the optimization and improvement of the vortex pump.
The 4 genotypes of hepatitis E virus (HEV) that infect humans (genotypes 1–4) vary in geographical distribution, transmission, and pathogenesis. Little is known about the properties of HEV or its ...hosts that contribute to these variations. Primary isolates grow poorly in cell culture; most studies have relied on variants adapted to cancer cell lines, which likely alter virus biology. We investigated the infection and replication of primary isolates of HEV in hepatocyte-like cells (HLCs) derived from human embryonic and induced pluripotent stem cells.
Using a cell culture–adapted genotype 3 strain and primary isolates of genotypes 1 to 4, we compared viral replication kinetics, sensitivity to drugs, and ability of HEV to activate the innate immune response. We studied HLCs using quantitative reverse-transcriptase polymerase chain reaction and immunofluorescence assay and enzyme-linked immunosorbent assays. We used an embryonic stem cell line that can be induced to express the CRISPR-Cas9 machinery to disrupt the peptidylprolyl isomerase A gene, encoding cyclophilin A (CYPA), a protein reported to inhibit replication of cell culture–adapted HEV. We further modified this line to rescue expression of CYPA before terminal differentiation to HLCs and performed HEV infection studies.
HLCs were permissive for infection by nonadapted, primary isolates of HEV genotypes 1 to 4. HEV infection of HLCs induced a replication-dependent type III interferon response. Replication of primary HEV isolates, unlike the cell culture–adapted strain, was not affected by disruption of the peptidylprolyl isomerase A gene or exposure to the CYPA inhibitor cyclosporine A.
Cell culture adaptations alter the replicative capacities of HEV. HLCs offer an improved, physiologically relevant, and genetically tractable system for studying the replication of primary HEV isolates. HLCs could provide a model to aid development of HEV drugs and a system to guide personalized regimens, especially for patients with chronic hepatitis E who have developed resistance to ribavirin.
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Purpose
The purpose of this paper is to investigate the clocking effect of impellers and the superposition between pump stages caused by clocking effect in a five-stage centrifugal pump. Then the ...best clocking scheme in terms of vibration is tried to be provided as well.
Design/methodology/approach
All curves of pressure fluctuation in different impeller stages can be divided into two groups for the difference of 1/16 T in time domain. The difference is mostly in vibration frequency and amplitude, little in pump head and efficiency.
Findings
All curves of pressure fluctuation in different impeller stages can be divided into two groups for the difference of 1/16 T in time domain. The difference is mostly in vibration frequency and amplitude, little in pump head and efficiency.
Research limitations/implications
This research involves eight different impeller clocking schemes. The results show that the clocking effect has little influence in pump head and efficiency, but the influence in pressure fluctuation is larger.
Practical implications
The paper provides guidance for the design of multistage pump for better vibration performance.
Originality/value
This research involves eight different impeller clocking schemes, the results show that the clocking effect has little influence in pump head and efficiency, but the influence in pressure fluctuation is larger. Then the best clocking scheme In terms of vibration is tried to be provided through analysis.
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