An N-terminal domain of adenovirus protein VI fragments membranes by inducing positive membrane curvature

Maier, Oana; Galan, Debra L.; Wodrich, Harald; Wiethoff, Christopher M.

doi:10.1016/j.virol.2010.03.043

Cited by 71 publications

(113 citation statements)

References 70 publications

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“…Here we report to our knowledge the first structure of protein VI, which plays multiple roles in the adenovirus life cycle-it functions as a cofactor for the adenovirus protease (AVP) and as a chaperone for nuclear transport, and is essential for virus assembly and endosome lysis (26)(27)(28)(29)(30). One copy of protein VI is found intimately associated with the base of each PPH on the capsid interior.…”

Section: Resultsmentioning

confidence: 99%

“…Most importantly, the structural models for VI and V provide insights into the need for proteolytic processing of VI so it can be released, in turn leading to partial exposure of the DNA. Proteolytic processing of VI is necessary for untethering and release of the membrane-lytic region, which is implicated in endosome lysis (29,30). Consistent with this cleavage requirement, abrogation of such processing of VI by the viral protease, as in the case of Adts1 mutant viruses, makes them noninfectious (37).…”

Section: Discussionmentioning

confidence: 98%

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Structures and organization of adenovirus cement proteins provide insights into the role of capsid maturation in virus entry and infection

Reddy¹,

Nemerow

2014

Proc. Natl. Acad. Sci. U.S.A.

118

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Adenovirus cement proteins play crucial roles in virion assembly, disassembly, cell entry, and infection. Based on a refined crystal structure of the adenovirus virion at 3.8-Å resolution, we have determined the structures of all of the cement proteins (IIIa, VI, VIII, and IX) and their organization in two distinct layers. We have significantly revised the recent cryoelectron microscopy models for proteins IIIa and IX and show that both are located on the capsid exterior. Together, the cement proteins exclusively stabilize the hexon shell, thus rendering penton vertices the weakest links of the adenovirus capsid. We describe, for the first time to our knowledge, the structure of protein VI, a key membrane-lytic molecule, and unveil its associations with VIII and core protein V, which together glue peripentonal hexons beneath the vertex region and connect them to the rest of the capsid on the interior. Following virion maturation, the cleaved N-terminal propeptide of VI is observed, reaching deep into the peripentonal hexon cavity, detached from the membrane-lytic domain, so that the latter can be released. Our results thus provide the molecular basis for the requirement of maturation cleavage of protein VI. This process is essential for untethering and release of the membrane-lytic region, which is known to mediate endosome rupture and delivery of partially disassembled virions into the host cell cytoplasm.human adenovirus | cement protein scaffold | structure-function relationships H uman adenoviruses (HAdVs) are large (∼150 nm in diameter, 150-MDa) nonenveloped double-stranded DNA (dsDNA) viruses that cause respiratory, ocular, and enteric diseases (1). Although these diseases are self-limiting in immunocompetent individuals, they cause significant morbidity in AIDS, cancer, and organ transplant patients with compromised immune systems (2-4). Because of their broad cell tropism and ease of genome manipulation, replication-deficient or conditionally replicating HAdVs are also being evaluated in the clinic as potential vaccine and gene therapy vectors (5).The capsid shell of an adenovirus (Ad) comprises multiple copies of three major capsid proteins (MCPs; hexon, penton base, and fiber) and four minor/cement proteins (IIIa, VI, VIII, and IX) that are organized with pseudo-T = 25 icosahedral symmetry ( Fig. 1 A and B). In addition, six other proteins (V, VII, μ, IVa2, terminal protein, and adenovirus protease) are encapsidated along with the 36-kb dsDNA genome inside the capsid (Fig. 1A). The crystal structures of all three MCPs are known, and so is their organization in the capsid from prior X-ray crystallography (6-8) and cryoelectron microscopy (cryo-EM) analyses (9, 10). Recently, high-resolution structures of recombinant HAdV5 vectors have been determined using cryo-EM (11) and X-ray methods (12) that revealed the structures and organization of some of the cement proteins. Both studies agree closely on the organization of the MCPs and confirm the earlier cryo-EM observations (9, 10, 13), but neither provided...

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 98%

Structures and organization of adenovirus cement proteins provide insights into the role of capsid maturation in virus entry and infection

Reddy¹,

Nemerow

2014

Proc. Natl. Acad. Sci. U.S.A.

118

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“…rhinovirus HRV2 and poliovirus) (Prchla et al, 1995), which also releases lysosomal content into the cytosol. Adenovirus membrane lytic protein VI ruptures the membrane by causing membrane curvature stress (Maier et al, 2010;Wiethoff et al, 2005), but membrane rupture can also be caused by vesicular swelling beyond the retaining capacity of the membrane. Alternatively, viral capsid proteins of HRV2 and poliovirus insert directly into the endolysosomal membrane and form size-selective pores (Fuchs and Blaas, 2010;Tosteson and Chow, 1997).…”

Section: Viral Proteinsmentioning

confidence: 99%

Lysosomal cell death at a glance

Aits

Jäättelä

2013

Journal of Cell Science

529

453

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Summary Lysosomes serve as the cellular recycling centre and are filled with numerous hydrolases that can degrade most cellular macromolecules. Lysosomal membrane permeabilization and the consequent leakage of the lysosomal content into the cytosol leads to so-called “lysosomal cell death”. This form of cell death is mainly carried out by the lysosomal cathepsin proteases and can have necrotic, apoptotic or apoptosis-like features depending on the extent of the leakage and the cellular context. This article summarizes our current knowledge on lysosomal cell death with an emphasis on the upstream mechanisms that lead to lysosomal membrane permeabilization.

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“…The cleaved C-terminal peptide serves as a coactivator of the viral protease (20,21). The N-terminal region of processed protein VI forms an amphipathic helix capable of membrane association and lysis in vitro and in vivo (18,22,23). Prior to assembly and in the assembled virion, the helix is shielded through association with hexons (12,24).…”

mentioning

confidence: 99%

The Amphipathic Helix of Adenovirus Capsid Protein VI Contributes to Penton Release and Postentry Sorting

Martinez

Schellenberger

Vasishtan

et al. 2015

J Virol

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Nuclear delivery of the adenoviral genome requires that the capsid cross the limiting membrane of the endocytic compartment and traverse the cytosol to reach the nucleus. This endosomal escape is initiated upon internalization and involves a highly coordinated process of partial disassembly of the entering capsid to release the membrane lytic internal capsid protein VI. Using wild-type and protein VI-mutated human adenovirus serotype 5 (HAdV-C5), we show that capsid stability and membrane rupture are major determinants of entry-related sorting of incoming adenovirus virions. Furthermore, by using electron cryomicroscopy, as well as penton-and protein VI-specific antibodies, we show that the amphipathic helix of protein VI contributes to capsid stability by preventing premature disassembly and deployment of pentons and protein VI. Thus, the helix has a dual function in maintaining the metastable state of the capsid by preventing premature disassembly and mediating efficient membrane lysis to evade lysosomal targeting. Based on these findings and structural data from cryo-electron microscopy, we suggest a refined disassembly mechanism upon entry. IMPORTANCEIn this study, we show the intricate connection of adenovirus particle stability and the entry-dependent release of the membrane-lytic capsid protein VI required for endosomal escape. We show that the amphipathic helix of the adenovirus internal protein VI is required to stabilize pentons in the particle while coinciding with penton release upon entry and that release of protein VI mediates membrane lysis, thereby preventing lysosomal sorting. We suggest that this dual functionality of protein VI ensures an optimal disassembly process by balancing the metastable state of the mature adenovirus particle.A denoviruses (AdVs) are nonenveloped, double-stranded DNA viruses that assemble in the nuclei of productively infected cells and are released at the end of the infection cycle into the extracellular milieu. Productive infection of new cells requires that the capsid follow a stepwise disassembly process upon entry that, if perfectly executed, results in highly efficient genome transfer to the nucleus (1, 2).The AdV virion is composed of 13 different polypeptides that form an icosahedral capsid encompassing the genome-containing viral core. The capsid is mainly composed of trimeric hexons building up the facets of the capsid. Pentons and fibers are located at each of the 12 vertices, where they form a pentameric penton base from which the trimeric fiber molecule elongates (3-5). In addition the capsid is stabilized via the cement proteins IIIa, VI, VIII, and IX. The capsid encloses the viral core, with the viral genome organized into chromatin through association with the major core protein VII and proteins V, X, TP, and IVa2 (3-5). Following (or concomitant with) capsid assembly, several of the virion proteins undergo proteolytic processing by the virion-incorporated adenoviral proteinase (AVP) (6). This process of virus maturation is essential to render ne...

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An N-terminal domain of adenovirus protein VI fragments membranes by inducing positive membrane curvature

Cited by 71 publications

References 70 publications

Structures and organization of adenovirus cement proteins provide insights into the role of capsid maturation in virus entry and infection

Structures and organization of adenovirus cement proteins provide insights into the role of capsid maturation in virus entry and infection

Lysosomal cell death at a glance

The Amphipathic Helix of Adenovirus Capsid Protein VI Contributes to Penton Release and Postentry Sorting

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