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: 4.44). 03/2011; 85(5):2386-96. DOI: 10.1128/JVI.01855-10
Source: PubMed


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


Available from: Christopher P. Walczak, Feb 20, 2014
  • Source
    • "Thus, despite being in the same protein family, distinct PDI members execute unique roles in priming SV40 for ER membrane transport. In the case of the murine PyV, a noncatalytic PDI family member called ERp29 acts in concert with ERp57 and PDI to remodel the VP1 C-terminal arm (Walczak & Tsai, 2011), destabilizing the viral structure to generate a hydrophobic virus (Magnuson et al., 2005); the human JC PyV was also reported to hijack the activities of the ERp57-PDI-ERp29 triad during infection (Nelson et al., 2012). Another virus reported to reach the ER during infection is the human papillomavirus (HPV) (Disbrow et al., 2005; Zhang et al., 2014), raising the possibility that HPV might also penetrate the ER membrane to access the cytosol during entry. "
    [Show abstract] [Hide abstract]
    ABSTRACT: A dedicated network of cellular factors ensures that proteins translocated into the endoplasmic reticulum (ER) are folded correctly before they exit this compartment en route to other cellular destinations or for secretion. When proteins misfold, selective ER-resident enzymes and chaperones are recruited to rectify the protein-misfolding problem in order to maintain cellular proteostasis. However, when a protein becomes terminally misfolded, it is ejected into the cytosol and degraded by the proteasome via a pathway called ER-associated degradation (ERAD). Strikingly, toxins and viruses can hijack elements of the ERAD pathway to access the host cytosol and cause infection. This review focuses on emerging data illuminating the molecular mechanisms by which these toxic agents co-opt the ER-to-cytosol translocation process to cause disease.
    Full-text · Article · Sep 2015 · Critical Reviews in Biochemistry and Molecular Biology
  • Source
    • "Virions are internalized into smooth endocytic vesicles [3], [6], [8], often positive for caveolin-1 [5], [6], and subsequently fuse with larger endosomes [3], [5], [6], [9]. Like other polyomaviruses, MPyV virions do not escape the endosomal system until they reach the lumen of smooth endoplasmic reticulum (ER) [5], [6], [9], [10], where lumenal enzymes facilitate virus capsid disassembly and uncoating of viral genomes prior to their import into the nucleus [11]–[13]. Regardless of the multiplicity of infection, only a few virions are able to deliver their genomic DNA into the cell nucleus [10]. Currently, two possible ways for viral genome delivery to the cell nucleus have been proposed: either partially disassembled virions translocate from ER to the cytosol and then are imported into the nucleus via nuclear pore complexes or, alternatively, they penetrate directly from ER to the nucleoplasm through the nuclear envelope (reviewed in [14]). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Infection of non-enveloped polyomaviruses depends on an intact microtubular network. Here we focus on mouse polyomavirus (MPyV). We show that the dynamics of MPyV cytoplasmic transport reflects the characteristics of microtubular motor-driven transport with bi-directional saltatory movements. In cells treated with microtubule-disrupting agents, localization of MPyV was significantly perturbed, the virus was retained at the cell periphery, mostly within membrane structures resembling multicaveolar complexes, and at later times post-infection, only a fraction of the virus was found in Rab7-positive endosomes and multivesicular bodies. Inhibition of cytoplasmic dynein-based motility by overexpression of dynamitin affected perinuclear translocation of the virus, delivery of virions to the ER and substantially reduced the numbers of infected cells, while overexpression of dominant-negative form of kinesin-1 or kinesin-2 had no significant impact on virus localization and infectivity. We also found that transport along microtubules was important for MPyV-containing endosome sequential acquisition of Rab5, Rab7 and Rab11 GTPases. However, in contrast to dominant-negative mutant of Rab7 (T22N), overexpression of dominant-negative mutant Rab11 (S25N) did not affect the virus infectivity. Altogether, our study revealed that MPyV cytoplasmic trafficking leading to productive infection bypasses recycling endosomes, does not require the function of kinesin-1 and kinesin-2, but depends on functional dynein-mediated transport along microtubules for translocation of the virions from peripheral, often caveolin-positive compartments to late endosomes and ER - a prerequisite for efficient delivery of the viral genome to the nucleus.
    Full-text · Article · May 2014 · PLoS ONE
  • 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.
    Preview · Article · Apr 2012 · Virology
Show more