MERS-CoV papain-like protease has deISGylating and deubiquitinating activities

Virology
Volumes 450–451, February 2014, Pages 64-70

Anna M. Mielech, Andy Kilianski, Yahira M. Baez-Santos, Andrew D. Mesecar, Susan C. Baker

Abstract

Coronaviruses encode papain-like proteases (PLpro) that are often multifunctional enzymes with protease activity to process the viral replicase polyprotein and deubiquitinating (DUB)/deISGylating activity, which is hypothesized to modify the innate immune response to infection. Here, we investigate the predicted DUB activity of the PLpro domain of the recently described Middle East Respiratory Syndrome Coronavirus (MERS-CoV). We found that expression of MERS-CoV PLpro reduces the levels of ubiquitinated and ISGylated host cell proteins; consistent with multifunctional PLpro activity. Further, we compared the ability of MERS-CoV PLpro and Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) PLpro to block innate immune signaling of proinflammatory cytokines. We show that expression of SARS-CoV and MERS-CoV PLpros blocks upregulation of cytokines CCL5, IFN-β and CXCL10 in stimulated cells. Overall these results indicate that the PLpro domains of MERS-CoV and SARS-CoV have the potential to modify the innate immune response to viral infection and contribute to viral pathogenesis.

Keywords

MERS-CoV, PLpro, DUB activity, Ubiquitin, deISGylating activity, ISG15

Tanshinones as selective and slow-binding inhibitors for SARS-CoV cysteine proteases

Bioorganic & Medicinal Chemistry
Volume 20, Issue 19, 1 October 2012, Pages 5928-5935

Ji-Young Park, Jang Hoon Kim, Young Min Kim, Hyung Jae Jeong, Dae Wook Kim, Ki Hun Park, Hyung-Jun Kwon, Su-Jin Park, Woo Song Lee, Young Bae Ryu

Abstract

In the search for anti-SARS-CoV, tanshinones derived from Salvia miltiorrhiza were found to be specific and selective inhibitors for the SARS-CoV 3CLpro and PLpro, viral cysteine proteases. A literature search for studies involving the seven isolated tanshinone hits showed that at present, none have been identified as coronaviral protease inhibitors. We have identified that all of the isolated tanshinones are good inhibitors of both cysteine proteases. However, their activity was slightly affected by subtle changes in structure and targeting enzymes. All isolated compounds (1–7) act as time dependent inhibitors of PLpro, but no improved inhibition was observed following preincubation with the 3CLpro. In a detail kinetic mechanism study, all of the tanshinones except rosmariquinone (7) were identified as noncompetitive enzyme isomerization inhibitors. However, rosmariquinone (7) showed a different kinetic mechanism through mixed-type simple reversible slow-binding inhibition. Furthermore, tanshinone I (5) exhibited the most potent nanomolar level inhibitory activity toward deubiquitinating (IC50 = 0.7 μM). Additionally, the inhibition is selective because these compounds do not exert significant inhibitory effects against other proteases including chymotrysin, papain, and HIV protease. These findings provide potential inhibitors for SARS-CoV viral infection and replication.

Keywords

Tanshinone, SARS-CoV, 3CLpro, PLpro, Slow-binding inhibitor