Hepatitis C virus and peroxisomes : evasion from the cellular antiviral response

Hepatitis C virus (HCV) causes the most prevalent viral infection worldwide. Upon infection, the HCV genome is detected by the RIG-I-MAVS signalling pathway leading to the production of direct antiviral effectors. NS3/4A protease is the main inhibitor of innate immunity against HCV and it was found to inhibit the mitochondrial signalling protein (MAVS). MAVS was recently found to localize at peroxisomes coordinating with mitochondria the activation of effective antiviral response. Peroxisomal MAVS is responsible for inducing a rapid but short termed antiviral response that is IFNindependent, contrary to mitochondrial MAVS which is associated with the activation of an IFN-dependent antiviral response with delayed kinetics. With this work we aimed at evaluating the effect of NS3/4A over the peroxisomal– MAVS pathway. Our results showed that the MAVS localizing exclusively at peroxisomes is targeted by the HCV NS3/4A protease. We also show that the MAVS cleavage by NS3/4A impaired the antiviral response mediated by peroxisomal-MAVS. These results reaffirm the importance of peroxisomes for viral-host interaction and in antiviral defences. Further studies are proposed in order to better understand the role of this organelle in innate immunity. These may lead to the improvement of therapy against HCV infection. palavras-chave Peroxissomas, Virus da Hepatite C, infeção viral, resposta antiviral celular, MAVS, NS3/4A resumo O vírus da hepatite C (VHC) provoca a infeção viral mais prevalente em todo o mundo. Após infeção, o genoma do VHC é detetado pela via de sinalização RIGI-MAVS levando à produção de efetores diretos da resposta antiviral. A protease NS3/4A é o principal inibidor da resposta imune produzido pelo VHC e foi descrito como inibidor da proteína MAVS. A proteína MAVS foi recentemente localizada nos peroxissomas que, juntamente com a mitocôndria, coordenam a resposta antiviral. A MAVS peroxisomal é responsável pela indução de uma resposta antiviral rápida mas de curta duração que é independente de interferões, mas pelo contrário, a MAVS mitocondrial está associada a uma ativação da resposta antiviral que é dependente de interferões mas que se caracteriza por uma cinética retardada. O nosso objetivo com este trabalho consistiu em avaliar o efeito da NS3/4A na via de sinalização coordenada pelos peroxissomas. Os nossos resultados mostram que a MAVS localizada nos peroxissomas é alvo da protease NS3/4A do VHC. Também mostramos que a clivagem da proteína MAVS pela NS3/4A inibe a resposta antiviral mediada pela MAVS peroxissomal. Estes resultados reafirmam a importância dos peroxissomas na interação vírushospedeiro e na defesa antiviral. Futuros estudos são aconselhados para que se compreenda a função dos peroxissomas na imunidade inata. Estes podem levar a uma melhoria na terapia da infeção pelo VHC. Hepatitis C virus and Peroxisomes: evasion from the cellular antiviral response 1 List of abbreviations aa amino acids acetyl-CoA acetyl coenzyme A AP-1 activator protein 1 ATP adenosine-5’-triphosphate CARD caspase activation and recruitment domain CARDIF card adaptor inducing IFN-β CLDN1 claudin-1 Cys Cysteine DAAs directing acting antiviral agents DC-SIGN dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin DLP1 dynamin-like protein 1 DNA deoxyribonucleic acid ds double-stranded ER endoplasmic reticulum ESCRTs endosomal sorting complex required for transport Fis1 mitochondrial fission 1 protein GAGs glycosaminoglycans H2O2 hydrogen peroxide HCV Hepatitis C virus IFNs Interferons IKK inhibitor of κB kinase IPS-1 IFN-β promoter stimulator 1 IRES internal ribosomal entry site IRF interferon regulator factor ISGs interferon-stimulated gene KO knock-out LD lipid droplet LDLR low-density lipoprotein receptor LGP2 laboratory of genetics and physiology 2 L-SIGN liver/lymph node-specific intercellular adhesion molecule-3-grabbing integrin LVPs lipoviral-particles Ana Rita Filgueiras Ferreira 2 MAM mitochondria-associated membranes MAVS mitochondrial antiviral signalling MDA5 melanoma differentiation-associated gene-5 MEF mouse embryonic fibroblast Mff mitochondrial-anchored protein ligase MTP microsomal transfer protein NF-κB nuclear factor kappa-light-chain-enhancer of activated B cell nt nucleotides PAMP pathogen-associated molecular pattern peg-IFN-α pegylated interferon α Pex Peroxin PMP peroxisomal membrane protein PPREs peroxisome proliferator response elements PRR pattern recognition receptor PPR peroxisome proliferator activated receptor PTS C-terminal peroxisomal targeting signal RdRp RNA-dependent RNA polymerase RIG-I retinoic acid-inducible gene I RLR RIG-I like receptors RNA ribonucleic acid RNS reactive nitrogen species ROS reactive oxygen species RXRs retinoid X receptors SR-BI scavenger receptor class B type I ss single-stranded SVR sustained virological response TBK1 TANK-binding kinase 1 TRAF tumor necrosis factor (TNF) receptor-associated factor UTR’s untranslated regions VISA virus-induced signalling adaptor VLCFAs very long chain fatty acids VLDL very-low-density-lipoproteins Hepatitis C virus and Peroxisomes: evasion from the cellular antiviral response