leupeptins and Herpes-Simplex

Herpes simplex virus-1 (HSV-1) is a double-stranded DNA virus that causes life-long infections. HSV-1 infections may lead to herpetic stromal keratitis that may advance to corneal blindness. HSV-1 infections can also cause fatal conditions, such as herpes encephalitis, or neonatal disease. A major virulence mechanism of HSV-1 is the control of autophagy, an innate immune defense strategy that could otherwise degrade viral particles. Here, to investigate a new mechanism for antiviral therapy, we tested the effect of various autophagy inducers (physiological and pharmacological) on infection. Autophagy stimulation was confirmed to significantly suppress HSV-1 infection in various cell types, without affecting cell viability. This study establishes the importance of autophagy for regulating HSV-1 infection, and provides a proof-of-principle evidence for a novel antiviral mechanism.

Topics: Adaptor Proteins, Signal Transducing; Animals; Autophagy; Cell Line; Cells, Cultured; Herpes Simplex; Herpesvirus 1, Human; Humans; Immunophenotyping; Leupeptins; Mice; Sequestosome-1 Protein

The PML protein is associated to nuclear bodies (NBs) whose functions are as yet unknown. PML and two other NBs-associated proteins, Sp100 And ISG20 are directly induced by interferons (IFN). PML and Sp100 proteins are covalently linked to SUMO-1, and ubiquitin-like peptide. PML NBs are disorganized in acute promyelocytic leukemia and during several DNA virus infections. In particular, the HSV-1 ICP0 protein is known to delocalize PML from NBs. Thus, NBs could play an important role in oncogenesis, IFN response and viral infections. Here, we show that HSV-1 induced PML protein degradation without altering its mRNA level. This degradation was time- and multiplicity of infection-dependent. Sp100 protein was also degraded, while another SUMO-1 conjugated protein, RanGAP1 and the IFN-induced protein kinase PKR were not. The proteasome inhibitor MG132 abrogated the HSV-1-induced PML and Sp100 degradation and partially restored their NB-localization. HSV-1 induced PML and Sp100 degradation constitutes a new example of viral inactivation of IFN target gene products.

Topics: Antigens, Nuclear; Autoantigens; Carrier Proteins; Cysteine Proteinase Inhibitors; GTPase-Activating Proteins; Herpes Simplex; Herpesvirus 1, Human; Humans; Interferons; Leupeptins; Molecular Weight; Neoplasm Proteins; Nuclear Proteins; Promyelocytic Leukemia Protein; Protein Kinases; RNA, Messenger; SUMO-1 Protein; Time Factors; Transcription Factors; Tumor Cells, Cultured; Tumor Suppressor Proteins; Ubiquitins