Contributions of the four essential entry glycoproteins to HSV-1 tropism and the selection of entry routes

Abstract

15Herpes Simplex viruses (HSV-1 and HSV-2) encode up to 15 glycosylated and unglycosylated 16 envelope proteins. Four of these, gB, gH, gL, and gD, are essential for entry and mediate cell-cell 17 fusion when co-expressed in uninfected, receptor-bearing cells. However, their contributions to 18 HSV-1 tropism and the selection of entry routes are unclear. To begin addressing this, we 19 previously pseudotyped VSV lacking its native glycoprotein, G, with HSV-1 glycoproteins gB, 20 gH, gL, and gD. This novel VSVDG-BHLD pseudotype recapitulated several aspects of HSV-1 21 entry: it could enter murine C10 cells, required gB, gH, gL, gD, and a cellular receptor for entry, 22 AUTHOR SUMMARY 37Different viruses enter cells by diverse routes, but how that choice is made is not always clear. 38Understanding the mechanisms behind these choices is vital for finding strategies to prevent viral 39 infections. In enveloped viruses, viral proteins embedded in the envelope accomplish this task. 40While most enveloped viruses encode one or two envelope proteins, Herpes Simplex viruses 41 (HSV) encode up to 15. Four of these are deemed essential for entry (gB, gH, gL, and gD) 42 whereas the rest have been termed non-essential. While these four proteins are essential, their 43 contributions to HSV-1 cellular tropism and entry pathways have not been fully elucidated. Here, 44we generated virions that have only the four essential HSV-1 glycoproteins on their surface. We 45show that the VSVDG-BHLD pseudotype has a narrower tropism than HSV-1 and uses different 46 entry pathways. Thus, the four essential HSV-1 entry glycoproteins alone do not define HSV-1 47 55All viruses must enter cells to initiate infection, and different viruses accomplish this task by 56 different mechanisms: some penetrate cells at the plasma membrane while others hijack host 57 endocytic pathways. Enveloped viruses -those in which the nucleocapsid is surrounded by a 58 cell-derived lipid bilayer -penetrate the cells by merging their lipid envelopes with a cellular 59 membrane, either the plasma membrane or the membrane of an endocytic vesicle following 60 endocytosis ( Fig 1) [reviewed in (1, 2)]. Viruses typically have preferred entry routes, the choice 61 of which is not always clear, and some enter different target cells by different routes. 62Understanding what routes viruses use to enter cells and how they select them may help inform 63 strategies to prevent viral infections. 64Herpes Simplex viruses (HSV-1 and HSV-2) are enveloped alphaherpesviruses that infect 65 much of the world's population for life, causing a panoply of diseases ranging from painful to 66 life-threatening (3, 4). An enduring mystery of HSV entry is how and why the virus enters 67 different cells by different routes: direct fusion with the plasma membrane [e.g., neurons, Vero 68 cells, Hep2 cells, reviewed in (5)] or by endocytosis and subsequent fusion with the endosomal 69 membrane [e.g., keratinocytes, corneal epithelial cells (6, 7)]. 70HSV-1 encodes 15 viral envelope proteins, ...

Host cell neddylation facilitates alphaherpesvirus entry in a virus-specific and cell-dependent manner

“…There are few if any host cell processes known to mediate the initial internalization step of HSV entry. Endocytic uptake of HSV can occur independently of clathrin, caveolin, cholesterol, and dynamin (22, 68, 92–97). We show that neddylation is integral to internalization of HSV-1 by endocytosis in B78-nectin-1 cells and human HaCaT cells.…”