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Journal of Virology, July 2009, p. 6825-6836, Vol. 83, No. 13
0022-538X/09/$08.00+0     doi:10.1128/JVI.00301-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Herpes Simplex Virus Glycoprotein B Associates with Target Membranes via Its Fusion Loops{triangledown}

Brian P. Hannah,1,{dagger} Tina M. Cairns,1,{dagger} Florent C. Bender,1 J. Charles Whitbeck,2 Huan Lou,1 Roselyn J. Eisenberg,2 and Gary H. Cohen1*

Department of Microbiology, School of Dental Medicine,1 Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 191042

Received 11 February 2009/ Accepted 10 April 2009

Herpes simplex virus (HSV) glycoproteins gB, gD, and gH/gL are necessary and sufficient for virus entry into cells. Structural features of gB are similar to those of vesicular stomatitis virus G and baculovirus gp64, and together they define the new class III group of fusion proteins. Previously, we used mutagenesis to show that three hydrophobic residues (W174, Y179, and A261) within the putative gB fusion loops are integral to gB function. Here we expanded our analysis, using site-directed mutagenesis of each residue in both gB fusion loops. Mutation of most of the nonpolar or hydrophobic amino acids (W174, F175, G176, Y179, and A261) had severe effects on gB function in cell-cell fusion and null virus complementation assays. Of the six charged amino acids, mutation of H263 or R264 also negatively affected gB function. To further analyze the mutants, we cloned the ectodomains of the W174R, Y179S, H263A, and R264A mutants into a baculovirus expression system and compared them with the wild-type (WT) form, gB730t. As shown previously, gB730t blocks virus entry into cells, suggesting that gB730t competes with virion gB for a cell receptor. All four mutant proteins retained this function, implying that fusion loop activity is separate from gB-receptor binding. However, unlike WT gB730t, the mutant proteins displayed reduced binding to cells and were either impaired or unable to bind naked, cholesterol-enriched liposomes, suggesting that it may be gB-lipid binding that is disrupted by the mutations. Furthermore, monoclonal antibodies with epitopes proximal to the fusion loops abrogated gB-liposome binding. Taken together, our data suggest that gB associates with lipid membranes via a fusion domain of key hydrophobic and hydrophilic residues and that this domain associates with lipid membranes during fusion.

* Corresponding author. Mailing address: Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104. Phone: (215) 898-6553. Fax: (215) 898-8385. E-mail: cohen{at}biochem.dental.upenn.edu

{triangledown} Published ahead of print on 15 April 2009.

{dagger} B.P.H. and T.M.C. contributed equally to this paper.

Journal of Virology, July 2009, p. 6825-6836, Vol. 83, No. 13
0022-538X/09/$08.00+0     doi:10.1128/JVI.00301-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Wang, J., Fan, Q., Satoh, T., Arii, J., Lanier, L. L., Spear, P. G., Kawaguchi, Y., Arase, H. (2009). Binding of Herpes Simplex Virus Glycoprotein B (gB) to Paired Immunoglobulin-Like Type 2 Receptor {alpha} Depends on Specific Sialylated O-Linked Glycans on gB. J. Virol. 83: 13042-13045 [Abstract] [Full Text]  
  • Wright, C. C., Wisner, T. W., Hannah, B. P., Eisenberg, R. J., Cohen, G. H., Johnson, D. C. (2009). Fusion between Perinuclear Virions and the Outer Nuclear Membrane Requires the Fusogenic Activity of Herpes Simplex Virus gB. J. Virol. 83: 11847-11856 [Abstract] [Full Text]  


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