Hepatitis C virus RNA replication is regulated by host geranylgeranylation and fatty acids

Abstract

Hepatitis C virus (HCV) infection is a major cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Our laboratory has previously demonstrated that high-level HCV replication during acute infection of chimpanzees is associated with the modulation of multiple genes involved in lipid metabolism, and that drugs that regulate cholesterol and fatty acid biosynthesis regulate the replication of the subgenomic HCV replicon in Huh-7 cells. In this article, we demonstrate that Huh-7 cells harboring replicating, full-length HCV RNAs express elevated levels of ATP citrate lyase and acetyl-CoA synthetase genes, both of which are involved in cholesterol and fatty acid biosynthesis. Further, we confirm that the cholesterol-biosynthetic pathway controls HCV RNA replication by regulating the cellular levels of geranylgeranyl pyrophosphate, we demonstrate that the impact of geranylgeranylation depends on the fatty acid content of the cell, and we show that fatty acids can either stimulate or inhibit HCV replication, depending on their degree of saturation. These results illustrate a complex cellular-regulatory network that controls HCV RNA replication, presumably by modulating the trafficking and association of cellular and͞or viral proteins with cellular membranes, suggesting that pharmacologic manipulation of these pathways may have a therapeutic effect in chronic HCV infection.cholesterol ͉ replicon H epatitis C virus (HCV), a member of the Flaviviridae family of viruses, is a major cause of chronic hepatitis and hepatocellular carcinoma (1, 2). The HCV genome is a positivestranded Ϸ9.6-kb RNA molecule consisting of a single ORF, which is flanked by 5Ј and 3Ј untranslated regions (UTR). The HCV 5Ј UTR contains a highly structured internal ribosome entry site (3-8), and the 3Ј UTR is essential for replication (9, 10). The HCV ORF encodes a single 3,008-to 3,037-aa polyprotein that is posttranslationally processed to produce Ն10 different proteins: core protein, envelope proteins E1 and E2, p7, and nonstructural proteins NS2, NS3, NS4A, NS4B, NS5A, and NS5B (1,8,11). Our understanding of the biology of HCV RNA replication has been greatly facilitated by the development of subgenomic and full-length HCV replicons that express HCV proteins and replicate their RNA in stably transfected human hepatoma-cell-derived Huh-7 cells.Our laboratory has previously demonstrated (12) that multiple cellular genes involved in lipid metabolism are differentially regulated during viral spread in acutely infected chimpanzees, and that ATP citrate lyase, which is required for cholesterol and fatty acid biosynthesis, is induced during the initial rise of high-level HCV replication during acute infection in chimpanzees. There is considerable evidence suggesting that the cholesterol and fatty-acid-biosynthesis pathways may play a role in HCV replication and infection. Steatosis, i.e., the formation of hepatocellular lipid droplets, is a well documented histological characteristic of HCV infection in humans, chimpanzees, and mouse m...

Serum cholesterol and statin use predict virological response to peginterferon and ribavirin therapy

“…The availability of fewer lipid rafts for replication seems to be a plausible explanation for at least some of the anti-HCV properties of statins. 32,33 The well-studied anti-inflammatory and immunomodulatory effects of statins with respect to cardiovascular and other organ systems may also explain the beneficial effects observed here in conjunction with PEG-IFN and RBV therapy. Peroxisome proliferatoractivated receptor alpha (PPAR-a) is a nuclear hormone receptor important in regulating lipid, cholesterol, carbohydrate, and steroid metabolism in the liver as well as the kidneys, heart, and skeletal muscle.…”

Study of changes in lipid profile and insulin resistance in Egyptian patients with chronic hepatitis C genotype 4 in the era of DAAs

“…The direct link between HCV and host lipoproteins explicates the significant interrelationship between HCV and host lipid metabolism, as proved both in vitro [17] and in clinical studies [12]. Meissner et al [12] reported a concomitant decrease in triglycerides and VLDL particle size and a marked increase in serum LDLc after 24 weeks of treating HCV genotype 1 infected patients with SOF/RBV, irrespective of the treatment outcome [12].…”

Hepatitis C virus selectively perturbs the distal cholesterol synthesis pathway in a genotype-specific manner

“…Thus, by demonstrating no genotype or SVR-related differences in lanosterol levels, we controlled for any potential differences preceding this step in the presqualene mevalonate pathway. We were consequently unable to address the role of the earlier isoprenoid pathway steps and processes (such as geranylgeranylation 14,38 ) that have been associated with viral replication, or alternative isoprenoid pathway products (such as prostaglandin and arachidonic acid). Importantly, however, we were able to address the late steps of cholesterol synthesis with a high degree of specificity, irrespective of possible earlier HCV interference in the sterol pathway.…”

“…13 Direct viral perturbation of cholesterol biosynthetic pathways and their regulation is suggested from experimental in vitro and animal models. [14][15][16][17][18] HCV-mediated oxidative stress has been suggested as a possible causative mechanism leading to both HCV-associated hepatic steatosis and IR, and has also been linked to cholesterol regulation. 15,19 Finally, from the host perspective, it is not known why compensatory regulation to increase cholesterol synthesis appears inadequate to resolve HCV-associated hypolipidemia.…”