title: Opposing effects of bacitracin on human papillomavirus type 16 infection: enhancement of binding and entry and inhibition of endosomal penetration.
abstract: Cell invasion by human papillomavirus type 16 (HPV16) is a complex process relying on multiple host cell factors. Here we describe an investigation into the role of cellular protein disulfide isomerases (PDIs) by studying the effects of the commonly used PDI inhibitor bacitracin on HPV16 infection. Bacitracin caused an unusual time-dependent opposing effect on viral infection. Enhanced cellular binding and entry were observed at early times of infection, while inhibition was observed at later times postentry. Bacitracin was rapidly taken up by host cells and colocalized with HPV16 at late times of infection. Bacitracin had no deleterious effect on HPV16 entry, capsid disassembly, exposure of L1/L2 epitopes, or lysosomal trafficking but caused a stark inhibition of L2/viral DNA (vDNA) endosomal penetration and accumulation at nuclear PML bodies. γ-Secretase has recently been implicated in the endosomal penetration of L2/vDNA, but bacitracin had no effect on γ-secretase activity, indicating that blockage of this step occurs through a γ-secretase-independent mechanism. Transient treatment with the reductant β-mercaptoethanol (β-ME) was able to partially rescue the virus from bacitracin, suggesting the involvement of a cellular reductase activity in HPV16 infection. Small interfering RNA (siRNA) knockdown of cellular PDI and the related PDI family members ERp57 and ERp72 reveals a potential role for PDI and ERp72 in HPV infection.
authors.affiliation: Department of Immunobiology, University of Arizona, Tucson, Arizona, USA. skcampos@email.arizona.edu
authors.forename: Samuel K
authors.initials: SK
authors.lastname: Campos
authors.forename: Janice A
authors.initials: JA
authors.lastname: Chapman
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Deymier
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Bronnimann
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Ozbun
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D000998:Antiviral Agents / Q000378:metabolism / Q000494:pharmacology*; D001414:Bacitracin / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D036022:Capsid Proteins / Q000737:chemistry / Q000276:immunology; D002460:Cell Line; D002466:Cell Nucleolus / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000187:drug effects* / Q000821:virology; D000939:Epitopes / Q000276:immunology; D016679:Genome, Viral; D052162:Human papillomavirus 16 / Q000187:drug effects* / Q000276:immunology; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D009856:Oncogene Proteins, Viral / Q000737:chemistry / Q000276:immunology; D019704:Protein Disulfide-Isomerases / Q000037:antagonists & inhibitors / Q000235:genetics; D019163:Reducing Agents / Q000494:pharmacology; D053586:Virus Internalization / Q000187:drug effects
chemical_list: D000998:Antiviral Agents; D036022:Capsid Proteins; D000939:Epitopes; C063316:L2 protein, Human papillomavirus type 16; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D019163:Reducing Agents; C062477:endoplasmic reticulum glycoprotein p72; D001414:Bacitracin; C063317:L1 protein, Human papillomavirus type 16; D053829:Amyloid Precursor Protein Secretases; D019704:Protein Disulfide-Isomerases