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2020 ; 94
(11
): ä Nephropedia Template TP
gab.com Text
Twit Text FOAVip
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English Wikipedia
Structure-Guided Mutagenesis Alters Deubiquitinating Activity and Attenuates
Pathogenesis of a Murine Coronavirus
#MMPMID32188728
Deng X
; Chen Y
; Mielech AM
; Hackbart M
; Kesely KR
; Mettelman RC
; O'Brien A
; Chapman ME
; Mesecar AD
; Baker SC
J Virol
2020[May]; 94
(11
): ä PMID32188728
show ga
Coronaviruses express a multifunctional papain-like protease, termed papain-like
protease 2 (PLP2). PLP2 acts as a protease that cleaves the viral replicase
polyprotein and as a deubiquitinating (DUB) enzyme which removes ubiquitin (Ub)
moieties from ubiquitin-conjugated proteins. Previous in vitro studies implicated
PLP2/DUB activity as a negative regulator of the host interferon (IFN) response,
but the role of DUB activity during virus infection was unknown. Here, we used
X-ray structure-guided mutagenesis and functional studies to identify amino acid
substitutions within the ubiquitin-binding surface of PLP2 that reduced DUB
activity without affecting polyprotein processing activity. We engineered a DUB
mutation (Asp1772 to Ala) into a murine coronavirus and evaluated the replication
and pathogenesis of the DUB mutant virus (DUBmut) in cultured macrophages and in
mice. We found that the DUBmut virus replicates similarly to the wild-type (WT)
virus in cultured cells, but the DUBmut virus activates an IFN response at
earlier times compared to the wild-type virus infection in macrophages,
consistent with DUB activity negatively regulating the IFN response. We compared
the pathogenesis of the DUBmut virus to that of the wild-type virus and found
that the DUBmut-infected mice had a statistically significant reduction
(P?0.05) in viral titer in liver and spleen at day 5 postinfection (d p.i.),
although both wild-type and DUBmut virus infections resulted in similar liver
pathology. Overall, this study demonstrates that structure-guided mutagenesis
aids the identification of critical determinants of the PLP2-ubiquitin complex
and that PLP2/DUB activity plays a role as an interferon antagonist in
coronavirus pathogenesis.IMPORTANCE Coronaviruses employ a genetic economy by
encoding multifunctional proteins that function in viral replication and also
modify the host environment to disarm the innate immune response. The coronavirus
papain-like protease 2 (PLP2) domain possesses protease activity, which cleaves
the viral replicase polyprotein, and also DUB activity (deconjugating
ubiquitin/ubiquitin-like molecules from modified substrates) using identical
catalytic residues. To separate the DUB activity from the protease activity, we
employed a structure-guided mutagenesis approach and identified residues that are
important for ubiquitin binding. We found that mutating the ubiquitin-binding
residues results in a PLP2 that has reduced DUB activity but retains protease
activity. We engineered a recombinant murine coronavirus to express the DUB
mutant and showed that the DUB mutant virus activated an earlier type I
interferon response in macrophages and exhibited reduced replication in mice. The
results of this study demonstrate that PLP2/DUB is an interferon antagonist and a
virulence trait of coronaviruses.