Dynamic interplay between the co-opted Fis1 mitochondrial fission protein and membrane contact site proteins in supporting tombusvirus replication

Plus-stranded RNA viruses have limited coding capacity and have to co-opt numerous pro-viral host factors to support their replication. Many of the co-opted host factors support the biogenesis of the viral replication compartments and the formation of viral replicase complexes on subverted subcellular membrane surfaces. Tomato bushy stunt virus (TBSV) exploits peroxisomal membranes, whereas the closely-related carnation Italian ringspot virus (CIRV) hijacks the outer membranes of mitochondria. How these organellar membranes can be recruited into pro-viral roles is not completely understood. Here, we show that the highly conserved Fis1 mitochondrial fission protein is co-opted by both TBSV and CIRV via direct interactions with the p33/p36 replication proteins. Deletion ofFIS1in yeast or knockdown of the homologous Fis1 in plants inhibits tombusvirus replication. Instead of the canonical function in mitochondrial fission and peroxisome division, the tethering function of Fis1 is exploited by tombusviruses to facilitate the subversion of membrane contact site (MCS) proteins and peroxisomal/mitochondrial membranes for the biogenesis of the replication compartment. We propose that the dynamic interactions of Fis1 with MCS proteins, such as the ER resident VAP tethering proteins, Sac1 PI4P phosphatase and the cytosolic OSBP-like oxysterol-binding proteins, promote the formation and facilitate the stabilization of virus-induced vMCSs, which enrich sterols within the replication compartment. We show that this novel function of Fis1 is exploited by tombusviruses to build nuclease-insensitive viral replication compartment.

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Co-opted Cellular Sac1 Lipid Phosphatase and PI(4)P Phosphoinositide Are Key Host Factors during the Biogenesis of the Tombusvirus Replication Compartment

Journal of Virology ◽

10.1128/jvi.01979-19 ◽

2020 ◽

Vol 94 (12) ◽

Cited By ~ 3

Author(s):

Zsuzsanna Sasvari ◽

Wenwu Lin ◽

Jun-Ichi Inaba ◽

Kai Xu ◽

Nikolay Kovalev ◽

...

Keyword(s):

Viral Replication ◽

Rna Viruses ◽

Critical Role ◽

Host Factors ◽

Positive Strand ◽

Content Type ◽

Membrane Contact Sites ◽

Viral Replicase ◽

Positive Strand Rna ◽

Replication Compartment

ABSTRACT Positive-strand RNA [(+)RNA] viruses assemble numerous membrane-bound viral replicase complexes (VRCs) with the help of viral replication proteins and co-opted host proteins within large viral replication compartments in the cytosol of infected cells. In this study, we found that deletion or depletion of Sac1 phosphatidylinositol 4-phosphate [PI(4)P] phosphatase reduced tomato bushy stunt virus (TBSV) replication in yeast (Saccharomyces cerevisiae) and plants. We demonstrate a critical role for Sac1 in TBSV replicase assembly in a cell-free replicase reconstitution assay. The effect of Sac1 seems to be direct, based on its interaction with the TBSV p33 replication protein, its copurification with the tombusvirus replicase, and its presence in the virus-induced membrane contact sites and within the TBSV replication compartment. The proviral functions of Sac1 include manipulation of lipid composition, sterol enrichment within the VRCs, and recruitment of additional host factors into VRCs. Depletion of Sac1 inhibited the recruitment of Rab5 GTPase-positive endosomes and enrichment of phosphatidylethanolamine in the viral replication compartment. We propose that Sac1 might be a component of the assembly hub for VRCs, likely in collaboration with the co-opted the syntaxin18-like Ufe1 SNARE protein within the TBSV replication compartments. This work also led to demonstration of the enrichment of PI(4)P phosphoinositide within the replication compartment. Reduction in the PI(4)P level due to chemical inhibition in plant protoplasts; depletion of two PI(4)P kinases, Stt4p and Pik1p; or sequestration of free PI(4)P via expression of a PI(4)P-binding protein in yeast strongly inhibited TBSV replication. Altogether, Sac1 and PI(4)P play important proviral roles during TBSV replication. IMPORTANCE Replication of positive-strand RNA viruses depends on recruitment of host components into viral replication compartments or organelles. Using TBSV, we uncovered the critical roles of Sac1 PI(4)P phosphatase and its substrate, PI(4)P phosphoinositide, in promoting viral replication. Both Sac1 and PI(4)P are recruited to the site of viral replication to facilitate the assembly of the viral replicase complexes, which perform viral RNA replication. We found that Sac1 affects the recruitment of other host factors and enrichment of phosphatidylethanolamine and sterol lipids within the subverted host membranes to promote optimal viral replication. In summary, this work demonstrates the novel functions of Sac1 and PI(4)P in TBSV replication in the model host yeast and in plants.

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Network-Guided Discovery of Influenza Virus Replication Host Factors

mBio ◽

10.1128/mbio.02002-18 ◽

2018 ◽

Vol 9 (6) ◽

Cited By ~ 14

Author(s):

Emily E. Ackerman ◽

Eiryo Kawakami ◽

Manami Katoh ◽

Tokiko Watanabe ◽

Shinji Watanabe ◽

...

Keyword(s):

Influenza Virus ◽

Viral Replication ◽

Virus Replication ◽

Drug Targets ◽

Antiviral Drug ◽

Viral Proteins ◽

Host Factors ◽

Ppi Network ◽

Host Proteins ◽

Influenza Virus Replication

ABSTRACTThe positions of host factors required for viral replication within a human protein-protein interaction (PPI) network can be exploited to identify drug targets that are robust to drug-mediated selective pressure. Host factors can physically interact with viral proteins, be a component of virus-regulated pathways (where proteins do not interact with viral proteins), or be required for viral replication but unregulated by viruses. Here, we demonstrate a method of combining human PPI networks with virus-host PPI data to improve antiviral drug discovery for influenza viruses by identifying target host proteins. Analysis shows that influenza virus proteins physically interact with host proteins in network positions significant for information flow, even after the removal of known abundance-degree bias within PPI data. We have isolated a subnetwork of the human PPI network that connects virus-interacting host proteins to host factors that are important for influenza virus replication without physically interacting with viral proteins. The subnetwork is enriched for signaling and immune processes distinct from those associated with virus-interacting proteins. Selecting proteins based on subnetwork topology, we performed an siRNA screen to determine whether the subnetwork was enriched for virus replication host factors and whether network position within the subnetwork offers an advantage in prioritization of drug targets to control influenza virus replication. We found that the subnetwork is highly enriched for target host proteins—more so than the set of host factors that physically interact with viral proteins. Our findings demonstrate that network positions are a powerful predictor to guide antiviral drug candidate prioritization.IMPORTANCEIntegrating virus-host interactions with host protein-protein interactions, we have created a method using these established network practices to identify host factors (i.e., proteins) that are likely candidates for antiviral drug targeting. We demonstrate that interaction cascades between host proteins that directly interact with viral proteins and host factors that are important to influenza virus replication are enriched for signaling and immune processes. Additionally, we show that host proteins that interact with viral proteins are in network locations of power. Finally, we demonstrate a new network methodology to predict novel host factors and validate predictions with an siRNA screen. Our results show that integrating virus-host proteins interactions is useful in the identification of antiviral drug target candidates.

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Extended synaptotagmin regulates membrane contact site structure and lipid transfer function in vivo

EMBO Reports ◽

10.15252/embr.202050264 ◽

2020 ◽

Vol 21 (9) ◽

Cited By ~ 1

Author(s):

Vaisaly R Nath ◽

Shirish Mishra ◽

Bishal Basak ◽

Deepti Trivedi ◽

Padinjat Raghu

Keyword(s):

Transfer Function ◽

Lipid Transfer ◽

Contact Site ◽

Site Structure ◽

Membrane Contact

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Susceptibility Genes to Plant Viruses

Viruses ◽

10.3390/v10090484 ◽

2018 ◽

Vol 10 (9) ◽

pp. 484 ◽

Cited By ~ 20

Author(s):

Hernan Garcia-Ruiz

Keyword(s):

Virus Replication ◽

Defense Responses ◽

Plant Viruses ◽

Host Factors ◽

Replication Proteins ◽

Replication Complex ◽

Virion Assembly ◽

Rna Translation ◽

Cellular Factors ◽

Genetically Determined

Plant viruses use cellular factors and resources to replicate and move. Plants respond to viral infection by several mechanisms, including innate immunity, autophagy, and gene silencing, that viruses must evade or suppress. Thus, the establishment of infection is genetically determined by the availability of host factors necessary for virus replication and movement and by the balance between plant defense and viral suppression of defense responses. Host factors may have antiviral or proviral activities. Proviral factors condition susceptibility to viruses by participating in processes essential to the virus. Here, we review current advances in the identification and characterization of host factors that condition susceptibility to plant viruses. Host factors with proviral activity have been identified for all parts of the virus infection cycle: viral RNA translation, viral replication complex formation, accumulation or activity of virus replication proteins, virus movement, and virion assembly. These factors could be targets of gene editing to engineer resistance to plant viruses.

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Listeria monocytogenes Exploits Mitochondrial Contact Site and Cristae Organizing System Complex Subunit Mic10 To Promote Mitochondrial Fragmentation and Cellular Infection

mBio ◽

10.1128/mbio.03171-19 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Filipe Carvalho ◽

Anna Spier ◽

Thibault Chaze ◽

Mariette Matondo ◽

Pascale Cossart ◽

...

Keyword(s):

Listeria Monocytogenes ◽

Mitochondrial Function ◽

Pathogenic Bacteria ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Host Cells ◽

Mitochondrial Network ◽

Contact Site ◽

Content Type ◽

Cell Functions

ABSTRACT Mitochondrial function adapts to cellular demands and is affected by the ability of the organelle to undergo fusion and fission in response to physiological and nonphysiological cues. We previously showed that infection with the human bacterial pathogen Listeria monocytogenes elicits transient mitochondrial fission and a drop in mitochondrion-dependent energy production through a mechanism requiring the bacterial pore-forming toxin listeriolysin O (LLO). Here, we performed quantitative mitochondrial proteomics to search for host factors involved in L. monocytogenes-induced mitochondrial fission. We found that Mic10, a critical component of the mitochondrial contact site and cristae organizing system (MICOS) complex, is significantly enriched in mitochondria isolated from cells infected with wild-type but not with LLO-deficient L. monocytogenes. Increased mitochondrial Mic10 levels did not correlate with upregulated transcription, suggesting a posttranscriptional mechanism. We then showed that Mic10 is necessary for L. monocytogenes-induced mitochondrial network fragmentation and that it contributes to L. monocytogenes cellular infection independently of MICOS proteins Mic13, Mic26, and Mic27. In conclusion, investigation of L. monocytogenes infection allowed us to uncover a role for Mic10 in mitochondrial fission. IMPORTANCE Pathogenic bacteria can target host cell organelles to take control of key cellular processes and promote their intracellular survival, growth, and persistence. Mitochondria are essential, highly dynamic organelles with pivotal roles in a wide variety of cell functions. Mitochondrial dynamics and function are intimately linked. Our previous research showed that Listeria monocytogenes infection impairs mitochondrial function and triggers fission of the mitochondrial network at an early infection stage, in a process that is independent of the presence of the main mitochondrial fission protein Drp1. Here, we analyzed how mitochondrial proteins change in response to L. monocytogenes infection and found that infection raises the levels of Mic10, a mitochondrial inner membrane protein involved in formation of cristae. We show that Mic10 is important for L. monocytogenes-dependent mitochondrial fission and infection of host cells. Our findings thus offer new insight into the mechanisms used by L. monocytogenes to hijack mitochondria to optimize host infection.

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Structural and Functional Characterization of Host FHL1 Protein Interaction with Hypervariable Domain of Chikungunya Virus nsP3 Protein

Journal of Virology ◽

10.1128/jvi.01672-20 ◽

2020 ◽

Vol 95 (1) ◽

Author(s):

Tetyana Lukash ◽

Tatiana Agback ◽

Francisco Dominguez ◽

Nikita Shiliaev ◽

Chetan Meshram ◽

...

Keyword(s):

Viral Replication ◽

Binding Site ◽

Cell Lines ◽

Binding Sites ◽

Chikungunya Virus ◽

Biological Significance ◽

Host Factors ◽

Published Data ◽

Wide Range ◽

Infection Spread

ABSTRACT Decades of insufficient control have resulted in unprecedented spread of chikungunya virus (CHIKV) around the globe, and millions have suffered from the highly debilitating disease. Nevertheless, the current understanding of CHIKV-host interactions and adaptability of the virus to replication in mosquitoes and mammalian hosts is still elusive. Our new study shows that four-and-a-half LIM domain protein (FHL1) is one of the host factors that interact with the hypervariable domain (HVD) of CHIKV nsP3. Unlike G3BPs, FHL1 is not a prerequisite of CHIKV replication, and many commonly used cell lines do not express FHL1. However, its expression has a detectable stimulatory effect(s) on CHIKV replication, and Fhl1 knockout (KO) cell lines demonstrate slower infection spread. Nuclear magnetic resonance (NMR)-based studies revealed that the binding site of FHL1 in CHIKV nsP3 HVD overlaps that of another proviral host factor, CD2AP. The structural data also demonstrated that FHL1-HVD interaction is mostly determined by the LIM1 domain of FHL1. However, it does not mirror binding of the entire protein, suggesting that other LIM domains are involved. In agreement with previously published data, our biological experiments showed that interactions of CHIKV HVD with CD2AP and FHL1 have additive effects on the efficiency of CHIKV replication. This study shows that CHIKV mutants with extensive modifications of FHL1- or both FHL1- and CD2AP-binding sites remain viable and develop spreading infection in multiple cell types. Our study also demonstrated that other members of the FHL family can bind to CHIKV HVD and thus may be involved in viral replication. IMPORTANCE Replication of chikungunya virus (CHIKV) is determined by a wide range of host factors. Previously, we have demonstrated that the hypervariable domain (HVD) of CHIKV nsP3 contains linear motifs that recruit defined families of host proteins into formation of functional viral replication complexes. Now, using NMR-based structural and biological approaches, we have characterized the binding site of the cellular FHL1 protein in CHIKV HVD and defined the biological significance of this interaction. In contrast to previously described binding of G3BP to CHIKV HVD, the FHL1-HVD interaction was found to not be a prerequisite of viral replication. However, the presence of FHL1 has a stimulatory effect on CHIKV infectivity and, subsequently, the infection spread. FHL1 and CD2AP proteins were found to have overlapping binding sites in CHIKV HVD and additive proviral functions. Elimination of the FHL1-binding site in the nsP3 HVD can be used for the development of stable, attenuated vaccine candidates.

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It Started With a Kiss: Monitoring Organelle Interactions and Identifying Membrane Contact Site Components in Plants

Frontiers in Plant Science ◽

10.3389/fpls.2020.00517 ◽

2020 ◽

Vol 11 ◽

Cited By ~ 1

Author(s):

Alice L. Baillie ◽

Anna-Lena Falz ◽

Stefanie J. Müller-Schüssele ◽

Imogen Sparkes

Keyword(s):

Contact Site ◽

Membrane Contact

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Host factors determine differential disease progression after infection with nef-deleted simian immunodeficiency virus

Journal of General Virology ◽

10.1099/vir.0.066563-0 ◽

2014 ◽

Vol 95 (10) ◽

pp. 2273-2284 ◽

Cited By ~ 2

Author(s):

Sieghart Sopper ◽

Kerstin Mätz-Rensing ◽

Thorsten Mühl ◽

Jonathan Heeney ◽

Christiane Stahl-Hennig ◽

...

Keyword(s):

Viral Load ◽

Viral Replication ◽

Disease Progression ◽

Simian Immunodeficiency Virus ◽

Mhc Class Ii ◽

Cell Activation ◽

Host Factors ◽

Immunological Parameters ◽

Set Point ◽

Immunodeficiency Virus

Infection of macaques with live attenuated simian immunodeficiency virus (SIV) usually results in long-lasting efficient protection against infection with pathogenic immunodeficiency viruses. However, attenuation by deletion of regulatory genes such as nef is not complete, leading to a high viral load and fatal disease in some animals. To characterize immunological parameters and polymorphic host factors, we studied 17 rhesus macaques infected with attenuated SIVmac239ΔNU. Eight animals were able to control viral replication, whereas the remaining animals (non-controllers) displayed variable set-point viral loads. Peak viral load at 2 weeks post-infection (p.i.) correlated significantly with set-point viral load (P<0.0001). CD4+ T-cell frequencies differed significantly soon after infection between controllers and non-controllers. Abnormal B-cell activation previously ascribed to Nef function could already be observed in non-controllers 8 weeks after infection despite the absence of Nef. Two non-controllers developed an AIDS-like disease within 102 weeks p.i. Virus from these animals transmitted to naïve animals replicated at low levels and the recipients did not develop immunodeficiency. This suggested that host factors determined differential viral load and subsequent disease course. Known Mhc class I alleles associated with disease progression in SIV WT infection only marginally influenced the viral load in Δnef-infected animals. Protection from SIVmac251 was associated with homozygosity for MHC class II in conjunction with a TLR7 polymorphism and showed a trend with initial viral replication. We speculated that host factors whose effects were usually masked by Nef were responsible for the different disease courses in individual animals upon infection with nef-deleted viruses.

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