Involvement of fatty acid synthase in dengue virus infection

Natthida Tongluan,Sittiruk Roytrakul,Duncan R Smith,Suwipa Ramphan,Nuttaporn Wongsiriroj,Sutee Yoksan,Phitchayapak Wintachai,Supoth Rajakam,Janthima Jaresitthikunchai,Nitwara Wikan,Sarawut Khongwichit

doi:10.1186/s12985-017-0685-9

Abstract

BackgroundThe mosquito transmitted Dengue virus (DENV) remains a significant public health problem in many tropical and subtropical countries. Increasing evidence has suggested that during the infection process cellular lipids play important roles at several stages of the replication cycle. This study sought to characterize the changes in lipid metabolism gene expression and investigated the role of one enzyme, fatty acid synthase, in DENV infection.MethodsTranscriptional profiles of genes associated with lipid metabolism were evaluated by real-time PCR after infection of different cell lines (HepG2 and HEK293T/17) and with different DENVs (laboratory adapted and low passage). Expression profiles of genes were evaluated by western blotting. A critical lipid metabolism protein, fatty acid synthase was down-regulated through siRNA and inhibited with orlistat and the effect on DENV infection determined by flow cytometry, plaque assay, western blotting and confocal microscopy.ResultsThe results showed alterations of gene transcription and expression were seen in genes variously associated with lipogenesis, lipolysis and fatty acid β-oxidation during DENV infection. Interference of fatty acid synthase with either siRNA or orlistat had marked effects on virus production, with orlistat having an EC50 value of 10.07 μM at 24 h post infection. However, non-structural protein expression was largely unaffected.ConclusionsWhile drug treatment reduced virus titer by up to 3Log10, no significant effect on DENV non-structural protein expression was observed, suggesting that fatty acid synthase acts through an effect on virion formation.

Highlights

The mosquito transmitted Dengue virus (DENV) remains a significant public health problem in many tropical and subtropical countries
Lipids in DENV infection To begin to investigate the involvement of lipids in DENV infection we first focused on neutral triglycerides
Evaluation of lipid pathway protein expression We further investigated changes in protein expression of genes involved in lipid metabolism, and levels of three proteins (ACC1, PPARγ and fatty acid synthase (FASN)) were determined by western blotting on days 1 to 3 post infection after infection with DENV-4LAB and DENV-4DHF or mock infection

Summary

Introduction

The mosquito transmitted Dengue virus (DENV) remains a significant public health problem in many tropical and subtropical countries. Each year there are believed to be nearly 400 million new Dengue virus (DENV) infections in tropical and sub-tropical countries worldwide, of which some 100 million show some form of symptom [1]. The DENV genome, a single stranded positive sense RNA molecule encoding a single open reading frame is directly translated as a single polypeptide that undergoes processing by viral and host proteases to generate the three structural proteins (envelope (E), pre-membrane (prM) and capsid proteins) and the seven non structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5) that form the replication complex [2]. The replication complex directs the production of the full length positive sense genome and the newly synthesized genomic RNA is packaged by the capsid protein forming a nucleocapsid complex [15]. As a consequence of this process, nearly 20% of the weight of the dengue virion is lipid [16]

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