Abstract
BackgroundThe homeostasis of lipid droplets (LDs) plays a crucial role in maintaining the physical metabolic processes in cells, and is regulated by many LD-associated proteins, including perilipin 5 (Plin5) in liver. As the putative sites of hepatitis C virus (HCV) virion assembly, LDs are vital to viral infection. In addition, the hepatic LD metabolism can be disturbed by non-structural HCV proteins, such as NS5A, but the details are still inexplicit.MethodsHCV NS5A was overexpressed in the livers and hepatocytes of wild-type and Plin5-null mice. BODIPY 493/503 and oil red O staining were used to detect the lipid content in mouse livers and hepatocytes. The levels of lipids, lipid peroxidation and inflammation biomarkers were further determined. Immunofluorescence assay and co-immunoprecipitation assay were performed to investigate the relationship of Plin5 and NS5A.ResultsOne week after adenovirus injection, livers expressing NS5A showed more inflammatory cell aggregation and more severe hepatic injuries in Plin5-null mice than in control mice, which was consistent with the increased serum levels of IL-2 and TNF-α (P < 0.05) observed in Plin5-null mice. Moreover, Plin5 deficiency in the liver and hepatocytes aggravated the elevation of MDA and 4-HNE levels induced by NS5A expression (P < 0.01). The triglyceride (TG) content was increased approximately 25% by NS5A expression in the wild-type liver and hepatocytes but was unchanged in the Plin5-null liver and hepatocytes. More importantly, Plin5 deficiency in the liver and hepatocytes exacerbated the elevation of non-esterified fatty acids (NEFAs) stimulated by NS5A expression (P < 0.05 and 0.01 respectively). Using triacsin C to block acyl-CoA biosynthesis, we found that Plin5 deficiency aggravated the NS5A-induced lipolysis of TG. In contrast, Plin5 overexpression in HepG2 cells ameliorated the NS5A-induced lipolysis and lipotoxic injuries. Immunofluorescent staining demonstrated that NS5A expression stimulated the targeting of Plin5 to the surface of the LDs in hepatocytes without altering the protein levels of Plin5. By co-IP, we found that the N-terminal domain (aa 32–128) of Plin5 was pivotal for its binding with NS5A.ConclusionsOur data highlight a protective role of Plin5 against hepatic lipotoxic injuries induced by HCV NS5A, which is helpful for understanding the steatosis and injuries in liver during HCV infection.
Highlights
The homeostasis of lipid droplets (LDs) plays a crucial role in maintaining the physical metabolic processes in cells, and is regulated by many LD-associated proteins, including perilipin 5 (Plin5) in liver
hepatitis C virus (HCV) RNA is replicated in special membranous structures, and the replication complex is recruited into adjacent lipid droplets (LDs) in a core-dependent way [5], the intracellular lipid levels and fatty acid composition have a strong influence on HCV life cycle
Plin5 deficiency aggravated HCV Non-structural protein 5A (NS5A)-induced hepatic injuries To investigate the role of Plin5 in HCV NS5A-induced lipid dysmetabolism, we administered 8-week-old male wild-type and Plin5-null mice adenovirus expressing NS5A by tail vein injection, and Ad-Null served as negative control
Summary
The homeostasis of lipid droplets (LDs) plays a crucial role in maintaining the physical metabolic processes in cells, and is regulated by many LD-associated proteins, including perilipin 5 (Plin5) in liver. The hepatic LD metabolism can be disturbed by non-structural HCV proteins, such as NS5A, but the details are still inexplicit. HCV hijacks host lipid metabolism and modulates the membrane dynamics to facilitate its own replication and assembly for its propagation [3]. All non-structural proteins are involved in HCV replication, NS5A is absolutely a central determinant in the replication complex [6, 7], and it has been reported to augment the transcriptional activity and gene expression of PPAR-γ to stimulate lipid accumulation [8]. As a member of the perilipin family, TIP47 promotes the maturation of LDs and regulates the incorporation of triglycerides (TGs) into LDs [12]
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