HSV Tegument Protein pUL51 Interacts with Host Dynactin for Viral Spread

Abstract

Dynein motors are microtubule associated protein complexes that mediate multiple essential cellular processes, such as long-distance cargo trafficking and stabilization of the microtubule organization center. Most of these functions and their regulations depend on the dynein motor subunit dynactin. By using an infection-inducible system, we disrupted dynein motor function after HSV entry by overexpressing a dominant-negative inhibitor of dynein, resulting in a 5-fold growth defect in Vero cells and 1000-fold growth defect in CAD neuronal cells. Also, we found that in infected CAD cells, the dynein complex was recruited to viral assembly sites regardless of microtubule polymerization. Based on these observations, we then identified a novel interaction between conserved HSV-1 tegument protein pUL51 and p150Glued. pUL51 is a palmitoylated Golgi membrane-associated protein that is required for efficient virus assembly and spread. Overexpression of pUL51 alone was sufficient to recruit p150Glued to Golgi membranes. Sequences that are important and sufficient for pUL51-p150Glued interaction were mapped to residues 90 to 124 in pUL51 and residues 548 to 911 in p150Glued. Deletion of a.a 90-124 in pUL51 resulted in a moderate viral growth defect, a profound spread defect, and failure to accumulate both dynactin and the viral spread factor glycoprotein E (gE) at cell-cell junctions. A synthetic peptide that contains pUL51 a.a 90-125 could also inhibit viral growth and spread in pUL51-dependent manner. Taken together, our results suggest that the proper function of pUL51 in efficient viral assembly and spread depends on its interaction with p150Glued. Author SummaryDuring their life-long infections, herpesviruses can spread within the human body in spite of a powerful immune response that includes antibodies that inactivate the virus. The virus accomplishes this by targeting its newly made infectious particles to junctions where infected cells meet their uninfected neighbors. Junctional targeting of virus particles requires that the virus hijack normal cellular machinery used for moving large cargoes within the cell, a process that is only partially understood. In this study, we have discovered a critical interaction between a virus protein that is present in all herpesviruses and a host cell cargo-moving protein that is required for virus spread between cells and shown that this interaction is common to several medically important human herpesviruses. We have also identified a short piece of this virus protein that is responsible for the interaction and shown that this short piece can be used to interrupt the interaction and prevent spread of herpes simplex virus (HSV) in cultured cells. Our study provides prove-of-concept evidence that the spread pathway of HSV, and possibly other herpesviruses, can be targeted for therapeutic purposes.