title: The herpes simplex virus type 1 UL20 protein and the amino terminus of glycoprotein K (gK) physically interact with gB.
abstract: Herpes simplex virus type 1 (HSV-1) glycoprotein K (gK) and the UL20 protein (UL20p) are strictly required for virus-induced cell fusion, and mutations within either the gK or UL20 gene cause extensive cell fusion (syncytium formation). We have shown that gK forms a functional protein complex with UL20p, which is required for all gK and UL20p-associated functions in the HSV-1 life cycle. Recently, we showed that the amino-terminal 82 amino acids (aa) of gK (gKa) were required for the expression of the syncytial phenotype of the mutant virus gBDelta28 lacking the carboxyl-terminal 28 amino acids of gB (V. N. Chouljenko, A. V. Iyer, S. Chowdhury, D. V. Chouljenko, and K. G. Kousoulas, J. Virol. 83:12301-12313, 2009). This work suggested that the amino terminus of gK may directly or indirectly interact with gB and/or other viral glycoproteins. Two-way coimmunoprecipitation experiments revealed that UL20p interacted with gB in infected cells. Furthermore, the gKa peptide was coimmunoprecipitated with gB but not gD. Three recombinant baculoviruses were constructed, expressing the amino-terminal 82 aa of gKa together with either the extracellular portion of gB (30 to 748 aa), gD (1 to 340 aa), or gH (1 to 792 aa), respectively. Coimmunoprecipitation experiments revealed that gKa physically interacted with the extracellular portions of gB and gH but not gD. Three additional recombinant baculoviruses expressing gKa and truncated gBs encompassing aa 30 to 154, 30 to 364, and 30 to 500 were constructed. Coimmunoprecipitation experiments showed that gKa physically interacted with all three truncated gBs. Computer-assisted prediction of possible gKa binding sites on gB suggested that gKa may interact predominantly with gB domain I (E. E. Heldwein, H. Lou, F. C. Bender, G. H. Cohen, R. J. Eisenberg, and S. C. Harrison, Science 313:217-220, 2006). These results imply that the gK/UL20p protein complex modulates the fusogenic properties of gB and gH via direct physical interactions.
authors.affiliation: Division of Biotechnology and Molecular Medicine, Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Chouljenko
authors.forename: Arun V
authors.initials: AV
authors.lastname: Iyer
authors.forename: Sona
authors.initials: S
authors.lastname: Chowdhury
authors.forename: Joohyun
authors.initials: J
authors.lastname: Kim
authors.forename: Konstantin G
authors.initials: KG
authors.lastname: Kousoulas
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D006561:Herpes Simplex / Q000821:virology*; D018259:Herpesvirus 1, Human / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: C121742:UL20 protein, Herpes simplex virus type 1; C072448:UL53 protein, Human herpesvirus 1; D014759:Viral Envelope Proteins; D014764:Viral Proteins; C040495:glycoprotein B, Simplexvirus