HEPATITIS C

The genotype 3-specific hepatitis C virus core protein residue phenylalanine 164 increases steatosis in an in vitro cellular model

C Hourioux¹, R Patient¹, A Morin¹, E Blanchard¹, A Moreau¹, S Trassard¹, B Giraudeau², P Roingeard¹

¹ Université François Rabelais, INSERM ERI 19 & CHRU de Tours, France
² Université François Rabelais, INSERM CIC 0202 & CHRU de Tours, France

Correspondence to:
Professor Philippe Roingeard
INSERM ERI 19, Laboratoire de Biologie Cellulaire, Faculté de Médecine, Université François Rabelais de Tours, 10 boulevard Tonnellé, F-37032 Tours Cedex, France; roingeard{at}med.univ-tours.fr

Background and aims: The prevalence and severity of liver steatosis are higher in patients infected with genotype 3 hepatitis C virus (HCV) than in patients infected with other genotypes. HCV core protein is known to affect lipid metabolism, inducing lipid droplet accumulation both in vitro and in vivo. An in vitro cellular model was used to investigate whether an HCV core protein with residues specific to genotype 3 increased this phenomenon.

Methods: Sequence comparisons for HCV core protein domain II, which is known to interact with lipid droplets, identified the phenylalanine (F) residue at position 164 as the only residue specific to genotype 3. The area covered by lipid droplets in sections of cells producing a wild-type genotype 1a HCV core protein was compared with that in cells producing a Y164F mutant protein.

Results: Cumulative lipid droplet area was significantly greater in sections of cells producing the Y164F mutant HCV core protein than in cells producing the wild-type protein (p<0.001). The frequency of cell sections containing more than 3 µm² of lipid droplets, in particular, was higher for the mutant than for the wild-type protein.

Conclusion: The data provide a molecular explanation for HCV genotype 3-specific lipid accumulation. This difference between genotypes may be due to phenylalanine having a higher affinity for lipids than tyrosine (Y). These observations provide useful information for further studies of the mechanisms involved in HCV-induced steatosis.

Abbreviations: aa, amino acid; apoB, apolipoprotein B; BSA, bovine serum albumin; EM, electron microscopy; ER, endoplasmic reticulum; ß-Gal, ß-galactosidase; HCV, hepatitis C virus; MTP, microsomal triglyceride transfer; PBS, phosphate-buffered saline; PBS-T, 0.05% (v/v) Tween 20 in PBS; PDI, protein disulphide isomerase; SFV, Semliki forest virus; SPP, signal peptide peptidase; VLDL, very low-density lipoprotein

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