HCV 3a Core Protein Increases Lipid Droplet Cholesteryl Ester Content via a Mechanism Dependent on Sphingolipid Biosynthesis

Abstract

Hepatitis C virus (HCV) infected patients often develop steatosis and the HCV core protein alone can induce this phenomenon. To gain new insights into the pathways leading to steatosis, we performed lipidomic profiling of HCV core protein expressing-Huh-7 cells and also assessed the lipid profile of purified lipid droplets isolated from HCV 3a core expressing cells. Cholesteryl esters, ceramides and glycosylceramides, but not triglycerides, increased specifically in cells expressing the steatogenic HCV 3a core protein. Accordingly, inhibitors of cholesteryl ester biosynthesis such as statins and acyl-CoA cholesterol acyl transferase inhibitors prevented the increase of cholesteryl ester production and the formation of large lipid droplets in HCV core 3a-expressing cells. Furthermore, inhibition of de novo sphingolipid biosynthesis by myriocin - but not of glycosphingolipid biosynthesis by miglustat - affected both lipid droplet size and cholesteryl ester level. The lipid profile of purified lipid droplets, isolated from HCV 3a core-expressing cells, confirmed the particular increase of cholesteryl ester. Thus, both sphingolipid and cholesteryl ester biosynthesis are affected by the steatogenic core protein of HCV genotype 3a. These results may explain the peculiar lipid profile of HCV-infected patients with steatosis.

Runx1 Role in Epithelial and Cancer Cell Proliferation Implicates Lipid Metabolism and Scd1 and Soat1 Activity

“…4B). Next, we inhibited expression of Scd1 and Soat1 using well-established small molecule chemical inhibitors (A939572) (41, 42) (57–59) and TMP-153 (43, 60, 61), respectively. A939572 inhibits both mouse and human Scd1respectively (62).…”

“…Scd1 inhibitor (A939572) (41, 42) was purchased from Med Chem, concentration of 1µM was used in experimental studies. Soat inhibitor TMP-153 sc-200649 (43) was purchased from Santa Cruz Biotechnology. Soat inhibitor diluted in keratinocyte media were added to experimental wells up to 0.5 µM concentration for 24 hours and equivalent dilutions of ethanol were added to control wells.…”

Seipin negatively regulates sphingolipid production at the ER–LD contact site

“…In contrast, various types of sphingolipids, in parallel with TAGs, were accumulated in various tissues of obese animals (Chaurasia and Summers, 2015;Iqbal et al, 2017). However, a discrepancy remains regarding the role of sphingolipid synthesis in LD formation (Loizides-Mangold et al, 2014;Tong et al, 2014;Xia et al, 2015;Alexaki et al, 2017). We took advantage of the LD induction system in yeast and found that LD biogenesis occurred when myriocin was added ( Fig.…”

Entangled in a membranous web: ER and lipid droplet reorganization during hepatitis C virus infection

“…HCV infection is often characterized by liver steatosis, a complex feature involving aberrant accumulation of LDs recapitulated in HCV-infected or core-expressing cells [46]. Steatosis is more frequently associated with HCV genotype 3, and genotype 3a core protein induces formation of large LDs by downregulating phosphatase and tensin homolog (PTEN) [81] or increasing LD cholesterol ester content with sphingolipid biosynthesis [82]. Core expression in mouse liver induces expression of sterol regulatory element binding protein 1c (SREBP-1c), a critical transcription factor in fatty acid, triglyceride, and phospholipid biosynthesis [83].…”