Host sphingolipid biosynthesis as a target for hepatitis C virus therapy

Abstract

An estimated 170 million individuals worldwide are infected with hepatitis C virus (HCV), a serious cause of chronic liver disease. Current interferon-based therapy for treating HCV infection has an unsatisfactory cure rate, and the development of more efficient drugs is needed. During the early stages of HCV infections, various host genes are differentially regulated, and it is possible that inhibition of host proteins affords a therapeutic strategy for treatment of HCV infection. Using an HCV subgenomic replicon cell culture system, here we have identified, from a secondary fungal metabolite, a lipophilic long-chain base compound, NA255 (1), a previously unknown small-molecule HCV replication inhibitor. NA255 prevents the de novo synthesis of sphingolipids, major lipid raft components, thereby inhibiting serine palmitoyltransferase, and it disrupts the association among HCV nonstructural (NS) viral proteins on the lipid rafts. Furthermore, we found that NS5B protein has a sphingolipid-binding motif in its molecular structure and that the domain was able to directly interact with sphingomyelin. Thus, NA255 is a new anti-HCV replication inhibitor that targets host lipid rafts, suggesting that inhibition of sphingolipid metabolism may provide a new therapeutic strategy for treatment of HCV infection.

Hepatitis c virus and host cell lipids: An intimate connection

“…73 Enzymatic activity of genotype 1b-derived NS5B might be stimulated by conformational changes that are triggered by sphingomyelin binding, 74 which also appears to contribute to NS5B localization in lipid rafts. 75 Accordingly, inhibition of sphingomyelin biosynthesis has been shown to inhibit genotype 1b, but not 2a RNA replication. 74,75 The HCV Replication Cycle and its Link to Lipids HCV modulates lipid metabolism and alters the endomembrane system to create a lipid-rich environment favorable for viral replication.…”

“…75 Accordingly, inhibition of sphingomyelin biosynthesis has been shown to inhibit genotype 1b, but not 2a RNA replication. 74,75 The HCV Replication Cycle and its Link to Lipids HCV modulates lipid metabolism and alters the endomembrane system to create a lipid-rich environment favorable for viral replication. Indeed, each step of the HCV replication cycle appears to be connected to host cell lipids (Fig.…”

Role of Membrane Rafts in Viral Infection

“…A lipophilic long-chain base compound, NA255, has been identified as a small-molecule HCV replication inhibitor from a secondary fungal metabolite. NA255 disrupts the association among HCV NS proteins on membrane rafts by prevention of de novo synthesis of sphingolipids, major membrane raft components [145]. Since cholesterol-depleted or sphingomyelinhydrolyzed virions lose ability of cellular internalization but not cell attachment, incorporation of cholesterol and sphingolipid into HCV particles is also important for virion maturation and infectivity.…”

“…Involvement of membrane rafts in viral RNA synthesis of enveloped viruses has been reported for HCV [143][144][145][146], respiratory syncytial virus (RSV; Paramyxoviridae) [147,148], DEN [149], and JEV [149]. Association of HCV nonstructural (NS) proteins with cholesterol-enriched membrane rafts in the Golgi-derived membrane forms the replication site of HCV RNA synthesis and protects it from RNase and protease [143,144].…”

Cellular models for the screening and development of anti-hepatitis C virus agents

“…Together with cholesterol, these lipids as well as glycosphingolipids enter into the composition of lipid rafts, the suspected site of HCV replication (Shi et al, 2003). Screening a natural product library with an HCV1b HTS replicon system, Sakamoto et al reported that inhibitors of serine palmitoyltransferase (the first step enzyme in sphingolipid biosynthesis) such as myriocin or NA255, inhibitors of dihydroceramide synthase (a further step in this pathway) such as fumonisin B1, and inhibitors of glycosphingolipid (GSL) synthesis such as PPMP all inhibited HCV replication (Sakamoto et al, 2005). The mechanism of this effect is £ To the best of their knowledge, authors have no real or perceived conflicts of interests.…”