๐ Inhibition of protein kinase R activation and upregulation of GADD34 expression play a synergistic role in facilitating coronavirus replication by maintaining de novo protein synthesis in virus-infected cells
A diversity of strategies is evolved by RNA viruses to manipulate the host translation machinery in order to create an optimal environment for viral replication and progeny production. One of the common viral targets is the ฮฑ subunit of eukaryotic initiation factor 2 (eIF-2ฮฑ). In this report, we show that phosphorylation of eIF-2ฮฑ was severely suppressed in human and animal cells infected with the coronavirus infectious bronchitis virus (IBV). To understand whether this suppression is through inhibition of protein kinase R (PKR), the double-stranded-RNA-dependent kinase that is one of the main kinases responsible for phosphorylation of eIF-2ฮฑ, cells infected with IBV were analyzed by Western blotting. The results showed that the level of phosphorylated PKR was greatly reduced in IBV-infected cells. Overexpression of IBV structural and nonstructural proteins (nsp) demonstrated that nsp2 is a weak PKR antagonist. Furthermore, GADD34, a component of the protein phosphatase 1 (PP1) complex, which dephosphorylates eIF-2ฮฑ, was significantly induced in IBV-infected cells. Inhibition of the PP1 activity by okadaic acid and overexpression of GADD34, eIF-2ฮฑ, and PKR, as well as their mutant constructs in virus-infected cells, showed that these viral regulatory strategies played a synergistic role in facilitating coronavirus replication. Taken together, these results confirm that IBV has developed a combination of two mechanisms, i.e., blocking PKR activation and inducing GADD34 expression, to maintain de novo protein synthesis in IBV-infected cells and, meanwhile, to enhance viral replication. Copyright ยฉ 2009, American Society for Microbiology.
keywords
๐ bronchitis virus (233)
๐ nonstructural proteins (57)
๐ virus replication (219)
๐ structural proteins (197)
๐ infected cells (307)
๐ infectious bronchitis (235)
๐ viral replication (258)
author
๐ค Wang, Xiaoxing
๐ค Liao, Ying
๐ค Yap, Pei Ling
๐ค Png, Kim J.
๐ค Tam, James P.
๐ค Liu, Ding Xiang
year
โฐ 2009
journal
๐ Journal of Virology
issn
๐ 0022538X
volume
83
number
23
page
12462-12472
citedbycount
42
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