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Amiloride is a competitive inhibitor of coxsackievirus B3 RNA polymerase.

ABSTRACT: Amiloride and its derivative 5-(N-ethyl-N-isopropyl)amiloride (EIPA) were previously shown to inhibit coxsackievirus B3 (CVB3) RNA replication in cell culture, with two amino acid substitutions in the viral RNA-dependent RNA polymerase 3D(pol) conferring partial resistance of CVB3 to these compounds (D. N. Harrison, E. V. Gazina, D. F. Purcell, D. A. Anderson, and S. Petrou, J. Virol. 82:1465-1473, 2008). Here we demonstrate that amiloride and EIPA inhibit the enzymatic activity of CVB3 3D(pol) in vitro, affecting both VPg uridylylation and RNA elongation. Examination of the mechanism of inhibition of 3D(pol) by amiloride showed that the compound acts as a competitive inhibitor, competing with incoming nucleoside triphosphates (NTPs) and Mg(2+). Docking analysis suggested a binding site for amiloride and EIPA in 3D(pol), located in close proximity to one of the Mg(2+) ions and overlapping the nucleotide binding site, thus explaining the observed competition. This is the first report of a molecular mechanism of action of nonnucleoside inhibitors against a picornaviral RNA-dependent RNA polymerase.

SUBMITTER: Gazina EV

PROVIDER: S-EPMC3196452 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Amiloride is a competitive inhibitor of coxsackievirus B3 RNA polymerase.

Gazina Elena V EV Smidansky Eric D ED Holien Jessica K JK Harrison David N DN Cromer Brett A BA Arnold Jamie J JJ Parker Michael W MW Cameron Craig E CE Petrou Steven S

Journal of virology 20110727 19

Amiloride and its derivative 5-(N-ethyl-N-isopropyl)amiloride (EIPA) were previously shown to inhibit coxsackievirus B3 (CVB3) RNA replication in cell culture, with two amino acid substitutions in the viral RNA-dependent RNA polymerase 3D(pol) conferring partial resistance of CVB3 to these compounds (D. N. Harrison, E. V. Gazina, D. F. Purcell, D. A. Anderson, and S. Petrou, J. Virol. 82:1465-1473, 2008). Here we demonstrate that amiloride and EIPA inhibit the enzymatic activity of CVB3 3D(pol) ...[more]

PMID: 21795353

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Project description:Coxsackievirus B3 (CVB3) is an enterovirus that causes diseases such as pancreatitis and myocarditis in humans. Approximately 10% of the CVB3 RNA genome consists of a highly structured 5' untranslated region (5' UTR) that is organized into six domains and contains a type I internal ribosome entry site (IRES). These features are common to all enteroviruses. Each RNA domain plays a vital role in translation and replication during the viral multiplication cycle. We used SHAPE-MaP chemistry to generate secondary structures of the 5' UTR from the avirulent strain CVB3/GA and the virulent strain CVB3/28. Our comparative models show how key nucleotide substitutions cause major restructuring of domains II and III of the 5' UTR in CVB3/GA. Despite these structural shifts, the molecule maintains several well-characterized RNA elements, which allows persistence of the unique avirulent strain. The results shed light on the 5' UTR regions serving as virulence determinants and those required for fundamental viral mechanisms. We used the SHAPE-MaP data to produce theoretical tertiary models using 3dRNA v2.0. These models suggest a compact conformation of the 5' UTR from the virulent strain CVB3/28 that brings critical domains into close contact. In contrast, the model of the 5' UTR from the avirulent strain CVB3/GA suggests a more extended conformation where the same critical domains are more separated. Our results suggest that the structure and orientation of RNA domains in the 5' UTR are responsible for low-efficiency translation, low viral titers, and absence of virulence observed during infection by CVB3/GA. IMPORTANCE Human enteroviruses, which include five different species and over 100 serotypes, are responsible for diseases ranging from mild respiratory infections to serious infections of pancreas, heart, and neural tissue. All enteroviral RNA genomes have a long and highly structured 5' untranslated region (5' UTR) containing an internal ribosome entry site (IRES). Major virulence determinants are located in the 5' UTR. We present RNA structure models that directly compare the 5' UTR derived from virulent and avirulent strains of the enterovirus coxsackievirus B3 (CVB3). The secondary-structure models show rearrangement of RNA domains known to be virulence determinants and conservation of structure in RNA elements known to be vital for translation and replication in the avirulent strain CVB3/GA. The tertiary-structure models reveal reorientation of RNA domains in CVB3/GA. Identifying the details of structure in these critical RNA domains will help direct antiviral approaches to this major human pathogen.

Project description:Group B coxsackieviruses are responsible for chronic cardiac infections. However, the molecular mechanisms by which the virus can persist in the human heart long after the signs of acute myocarditis have abated are still not completely understood. Recently, coxsackievirus B3 strains with 5'-terminal deletions in genomic RNAs were isolated from a patient suffering from idiopathic dilated cardiomyopathy, suggesting that such mutant viruses may be the forms responsible for persistent infection. These deletions lacked portions of 5' stem-loop I, which is an RNA secondary structure required for viral RNA replication. In this study, we assessed the consequences of the genomic deletions observed in vivo for coxsackievirus B3 biology. Using cell extracts from HeLa cells, as well as transfection of luciferase replicons in two types of cardiomyocytes, we demonstrated that coxsackievirus RNAs harboring 5' deletions ranging from 7 to 49 nucleotides in length can be translated nearly as efficiently as those of wild-type virus. However, these 5' deletions greatly reduced the synthesis of viral RNA in vitro, which was detected only for the 7- and 21-nucleotide deletions. Since 5' stem-loop I RNA forms a ribonucleoprotein complex with cellular and viral proteins involved in viral RNA replication, we investigated the binding of the host cell protein PCBP2, as well as viral protein 3CDpro, to deleted positive-strand RNAs corresponding to the 5' end. We found that binding of these proteins was conserved but that ribonucleoprotein complex formation required higher PCBP2 and 3CDpro concentrations, depending on the size of the deletion. Overall, this study confirmed the characteristics of persistent CVB3 infection observed in heart tissues and provided a possible explanation for the low level of RNA replication observed for the 5'-deleted viral genomes-a less stable ribonucleoprotein complex formed with proteins involved in viral RNA replication.IMPORTANCE Dilated cardiomyopathy is the most common indication for heart transplantation worldwide, and coxsackie B viruses are detected in about one-third of idiopathic dilated cardiomyopathies. Terminal deletions at the 5' end of the viral genome involving an RNA secondary structure required for RNA replication have been recently reported as a possible mechanism of virus persistence in the human heart. These mutations are likely to disrupt the correct folding of an RNA secondary structure required for viral RNA replication. In this report, we demonstrate that transfected RNAs harboring 5'-terminal sequence deletions are able to direct the synthesis of viral proteins, but not genomic RNAs, in human and murine cardiomyocytes. Moreover, we show that the binding of cellular and viral replication factors to viral RNA is conserved despite genomic deletions but that the impaired RNA synthesis associated with terminally deleted viruses could be due to destabilization of the ribonucleoprotein complexes formed.

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Amiloride is a competitive inhibitor of coxsackievirus B3 RNA polymerase.

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Amiloride is a competitive inhibitor of coxsackievirus B3 RNA polymerase.

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