Article

A PDI family network acts distinctly and coordinately with ERp29 to facilitate Polyomavirus infection

Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
Journal of Virology (Impact Factor: 4.65). 03/2011; 85(5):2386-96. DOI: 10.1128/JVI.01855-10
Source: PubMed

ABSTRACT Endoplasmic reticulum (ER)-to-cytosol membrane transport is a decisive infection step for the murine polyomavirus (Py). We previously determined that ERp29, a protein disulfide isomerase (PDI) member, extrudes the Py VP1 C-terminal arm to initiate ER membrane penetration. This reaction requires disruption of Py's disulfide bonds. Here, we found that the PDI family members ERp57, PDI, and ERp72 facilitate virus infection. However, while all three proteins disrupt Py's disulfide bonds in vitro, only ERp57 and PDI operate in concert with ERp29 to unfold the VP1 C-terminal arm. An alkylated Py cannot stimulate infection, implying a pivotal role of viral free cysteines during infection. Consistent with this, we found that although PDI and ERp72 reduce Py, ERp57 principally isomerizes the virus in vitro, a reaction that requires viral free cysteines. Our mutagenesis study subsequently identified VP1 C11 and C15 as important for infection, suggesting a role for these residues during isomerization. C11 and C15 also act together to stabilize interpentamer interactions for a subset of the virus pentamers, likely because some of these residues form interpentamer disulfide bonds. This study reveals how a PDI family functions coordinately and distinctly to promote Py infection and pinpoints a role of viral cysteines in this process.

Download full-text

Full-text

Available from: Christopher P. Walczak, Feb 20, 2014
0 Followers
 · 
116 Views
  • Source
    • "In SV40 , cysteine 9 ( C9 ) and C104 form inter - pentameric disulfide bonds with adjacent pentamers to link the capsid together , and a disulfide bond at C15 has been shown to be important in mPy ( Schelhaas et al . , 2007 ; Walczak and Tsai , 2011 ) . Cysteine residues 104 and 257 are conserved in JCV ; however , JCV lacks the C9 , and likely engages these ER enzymes in a similar , but not identical fashion . "
    [Show abstract] [Hide abstract]
    ABSTRACT: JC polyomavirus (JCV) is an important human pathogen that causes the fatal demyelinating disease progressive multifocal leukoencephalopathy (PML). In this study we further delineate the early events of JCV entry in human glial cells and demonstrate that a pentameric subunit of the viral capsid is able to recapitulate early events in viral trafficking. We show that JCV traffics to the endoplasmic reticulum (ER) by 6h post infection, and that VP1 pentamers arrive at the ER with similar kinetics. Further, this JCV localization to the ER is critical for infection, as treatment of cells with agents that prevent ER trafficking, ER function, or ER quality control reduce JCV infectivity. These pentamers represent a new tool to study polyomavirus entry, and will be particularly useful in studying recently identified polyomaviruses that are difficult to propagate.
    Virology 04/2012; 428(1):30-40. DOI:10.1016/j.virol.2012.03.014 · 3.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Many viruses and toxins disassemble to enter host cells and cause disease. These conformational changes must be orchestrated temporally and spatially during entry to avoid premature disassembly leading to nonproductive pathways. Although viruses and toxins are evolutionarily distinct toxic agents, emerging findings in their respective fields have revealed that the cellular locations supporting disassembly, the host factors co-opted during disassembly, the nature of the conformational changes, and the physiological function served by disassembly are strikingly conserved. Here, we examine some of the shared disassembly principles observed in model viruses and toxins. Where appropriate, we also underscore their differences. Our major intention is to draw together the fields of viral and toxin cell entry by using lessons gleaned from each field to inform and benefit one another.
    Annual review of microbiology 06/2011; 65(1):287-305. DOI:10.1146/annurev-micro-090110-102855 · 13.02 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Protein misfolding within the endoplasmic reticulum (ER) is managed by an ER quality control system that retro-translocates aberrant proteins into the cytosol for proteasomal destruction. This process, known as ER-associated degradation, utilizes the action of ER redox enzymes to accommodate the disulfide-bonded nature of misfolded proteins. Strikingly, various pathogenic viruses and toxins co-opt these redox components to reach the cytosol during entry. These redox factors thus regulate critical cellular homeostasis and host-pathogen interactions. RECENT ADVANCES: Recent studies identify specific members of the protein disulfide isomerase (PDI) family, which use their chaperone and catalytic activities, in engaging both misfolded ER proteins and pathogens. The precise molecular mechanism by which a dedicated PDI family member disrupts the disulfide bonds in the misfolded ER proteins and pathogens, as well as how they act to unfold these substrates to promote their ER-to-cytosol membrane transport, remain poorly characterized. How PDI family members distinguish folded versus misfolded ER substrates remains enigmatic. What physical characteristics surrounding a substrate's disulfide bond instruct PDI that it is mispaired or native? For the pathogens, as their disulfide bonds normally serve a critical role in providing physical support, what conformational changes experienced in the host enable their disulfide bonds to be disrupted? A combination of more rigorous biochemical and high-resolution structural studies should begin to address these questions.
    Antioxidants & Redox Signaling 12/2011; 16(8):809-18. DOI:10.1089/ars.2011.4425 · 7.67 Impact Factor
Show more