Distinct roles in folding, CD81 receptor binding and viral entry for conserved histidine residues of hepatitis C virus glycoprotein E1 and E2

2012 ◽  
Vol 443 (1) ◽  
pp. 85-94 ◽  
Author(s):  
Irene Boo ◽  
Kevin teWierik ◽  
Florian Douam ◽  
Dimitri Lavillette ◽  
Pantelis Poumbourios ◽  
...  

The protonation of histidine in acidic environments underpins its role in regulating the function of pH-sensitive proteins. For pH-sensitive viral fusion proteins, histidine protonation in the endosome leads to the activation of their membrane fusion function. The HCV (hepatitis C virus) glycoprotein E1–E2 heterodimer mediates membrane fusion within the endosome, but the roles of conserved histidine residues in the formation of a functional heterodimer and in sensing pH changes is unknown. We examined the functional roles of conserved histidine residues located within E1 and E2. The E1 mutations, H222A/R, H298R and H352A, disrupted E1–E2 heterodimerization and reduced virus entry. A total of five out of six histidine residues located within the E2 RBD (receptor-binding domain) were important for the E2 fold, and their substitution with arginine or alanine caused aberrant heterodimerization and/or CD81 binding. Distinct roles in E1–E2 heterodimerization and in virus entry were identified for His691 and His693 respectively within the membrane-proximal stem region. Viral entry and cell–cell fusion at neutral and low pH values were enhanced with H445R, indicating that the protonation state of His445 is a key regulator of HCV fusion. However, H445R did not overcome the block to virus entry induced by bafilomycin A1, indicating a requirement for an endosomal activation trigger in addition to acidic pH.

2007 ◽  
Vol 18 (4) ◽  
pp. 169-189 ◽  
Author(s):  
Pantelis Poumbourios ◽  
Heidi E Drummer

Improvements to antiviral therapies for the treatment of hepatitis C virus (HCV) infections will require the use of multiple drugs that target viral proteins essential for replication. The discovery of anti-HCV compounds has been severely hampered by the lack of cell culture replication systems. Since the late 1990s, the advent of sub-genomic replicons that model the intracellular events leading to HCV genome replication have enabled the discovery of HCV protease and polymerase inhibitors, but did not allow the study of HCV entry or entry inhibitors. More recently, retroviral pseudotyping of the viral glycoproteins and the development of a cell culture-based system that recapitulates the entire HCV replication cycle were achieved. These new experimental systems have enabled a rapid advance in our knowledge of how HCV glycoproteins, E1 and E2, mediate receptor binding and viral entry. These systems have facilitated the discovery of a range of viral receptors. Evidence is emerging that CD81, scavenger receptor class B type I, claudin-1 and the low-density lipoprotein receptor are involved in viral entry. In addition, DC-SIGN and L-SIGN may function to internalize virus into dendritic or endothelial cells, facilitating the transport of virions to sites of infection such as the liver. This review focuses on the interaction between the HCV glycoproteins and cellular receptors, and our current understanding of the viral entry pathway. In addition, key questions on the role that these receptors play in viral entry are raised and potential avenues for the discovery of new antiviral agents are highlighted.


2008 ◽  
Vol 135 (5) ◽  
pp. 1719-1728.e1 ◽  
Author(s):  
Anita Haberstroh ◽  
Eva K. Schnober ◽  
Mirjam B. Zeisel ◽  
Patric Carolla ◽  
Heidi Barth ◽  
...  

2008 ◽  
Vol 48 ◽  
pp. S226
Author(s):  
A. Haberstroh ◽  
E.K. Schnober ◽  
P. Carolla ◽  
M.B. Zeisel ◽  
H. Barth ◽  
...  

2008 ◽  
Vol 83 (4) ◽  
pp. 2011-2014 ◽  
Author(s):  
Shufeng Liu ◽  
Wei Yang ◽  
Le Shen ◽  
Jerrold R. Turner ◽  
Carolyn B. Coyne ◽  
...  

ABSTRACT A tight junction (TJ) protein, claudin-1 (CLDN1), was identified recently as a key factor for hepatitis C virus (HCV) entry. Here, we show that another TJ protein, occludin, is also required for HCV entry. Mutational study of CLDN1 revealed that its tight junctional distribution plays an important role in mediating viral entry. Together, these data support the model in which HCV enters liver cells from the TJ. Interestingly, HCV infection of Huh-7 hepatoma cells downregulated the expression of CLDN1 and occludin, preventing superinfection. The altered TJ protein expression may contribute to the morphological and functional changes observed in HCV-infected hepatocytes.


2020 ◽  
Vol 883 ◽  
pp. 173323 ◽  
Author(s):  
Xiao-Qin Lv ◽  
Li-Li Zou ◽  
Jia-Li Tan ◽  
Hu Li ◽  
Jian-Rui Li ◽  
...  

2020 ◽  
Vol 21 (6) ◽  
pp. 2091 ◽  
Author(s):  
Che Colpitts ◽  
Pei-Ling Tsai ◽  
Mirjam Zeisel

Hepatitis C virus (HCV) is a major cause of chronic hepatitis and liver disease worldwide. Its tissue and species tropism are largely defined by the viral entry process that is required for subsequent productive viral infection and establishment of chronic infection. This review provides an overview of the viral and host factors involved in HCV entry into hepatocytes, summarizes our understanding of the molecular mechanisms governing this process and highlights the therapeutic potential of host-targeting entry inhibitors.


2020 ◽  
Vol 27 (7) ◽  
pp. 780-792.e5 ◽  
Author(s):  
Zongyi Hu ◽  
Adam Rolt ◽  
Xin Hu ◽  
Christopher D. Ma ◽  
Derek J. Le ◽  
...  

2006 ◽  
Vol 80 (16) ◽  
pp. 7844-7853 ◽  
Author(s):  
Heidi E. Drummer ◽  
Irene Boo ◽  
Anne L. Maerz ◽  
Pantelis Poumbourios

ABSTRACT The hepatitis C virus (HCV) glycoproteins E1 and E2 form a heterodimer that mediates CD81 receptor binding and viral entry. In this study, we used site-directed mutagenesis to examine the functional role of a conserved G436WLAGLFY motif of E2. The mutants could be placed into two groups based on the ability of mature virion-incorporated E1E2 to bind the large extracellular loop (LEL) of CD81 versus the ability to mediate cellular entry of pseudotyped retroviral particles. Group 1 comprised E2 mutants where LEL binding ability largely correlated with viral entry ability, with conservative and nonconservative substitutions (W437 L/A, L438A, L441V/F, and F442A) inhibiting both functions. These data suggest that Trp-437, Leu-438, Leu-441, and Phe-442 directly interact with the LEL. Group 2 comprised E2 glycoproteins with more conservative substitutions that lacked LEL binding but retained between 20% and 60% of wild-type viral entry competence. The viral entry competence displayed by group 2 mutants was explained by residual binding by the E2 receptor binding domain to cellular full-length CD81. A subset of mutants maintained LEL binding ability in the context of intracellular E1E2 forms, but this function was largely lost in virion-incorporated glycoproteins. These data suggest that the CD81 binding site undergoes a conformational transition during glycoprotein maturation through the secretory pathway. The G436P mutant was an outlier, retaining near-wild-type levels of CD81 binding but lacking significant viral entry ability. These findings indicate that the G436WLAGLFY motif of E2 functions in CD81 binding and in pre- or post-CD81-dependent stages of viral entry.


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