Akt Plays a Critical Role in Replication of Nonsegmented Negative-Stranded RNA Viruses

Here, we report that specific manipulations of the cellular response to virus infection can cause prevention of apoptosis and consequent establishment of persistent infection. Infection of several human cell lines with Sendai virus (SeV) or human parainfluenza virus 3, two prototypic paramyxoviruses, caused slow apoptosis, which was markedly accelerated upon blocking the action of phosphatidylinositol 3-kinases (PI3 kinases) in the infected cells. The observed apoptosis required viral gene expression and the action of the caspase 8 pathway. Although virus infection activated PI3 kinase, as indicated by AKT activation, its blockage did not inhibit JNK activation or IRF-3 activation. The action of neither the Jak-STAT pathway nor the NF-B pathway was required for apoptosis. In contrast, IRF-3 activation was essential, although induction of the proapototic protein TRAIL by IRF-3 was not required. When IRF-3 was absent or its activation by the RIG-I pathway was blocked, SeV established persistent infection, as documented by viral protein production and infectious virus production. Introduction of IRF-3 in the persistently infected cells restored the cells' ability to undergo apoptosis. These results demonstrated that in our model system, IRF-3 controlled the fate of the SeV-infected cells by promoting apoptosis and preventing persistence.

Section: Discussionmentioning

confidence: 99%

“…The involvement of the NF-B pathway in this action remains controversial (26). Recently, it has been reported that Akt activity is also required for optimal replication of paramyxoviruses and other nonsegmented negative-strand viruses (32).…”

mentioning

confidence: 99%

IRF-3 Activation by Sendai Virus Infection Is Required for Cellular Apoptosis and Avoidance of Persistence

Peters

Chattopadhyay

Sen

2008

“…Sun et al (53) recently reported that PIV5 V protein interacts with Akt, a serine/threonine kinase, and Akt plays a critical role in PIV5 replication. We have examined the interaction of the hPIV2 V and Akt.…”

Section: Discussionmentioning

confidence: 99%

Human Parainfluenza Virus Type 2 V Protein Inhibits Genome Replication by Binding to the L Protein: Possible Role in Promoting Viral Fitness

Nishio

Ohtsuka

Tsurudome

et al. 2008

The human parainfluenza virus type 2 (hPIV2) V protein plays important roles in inhibiting the host interferon response and promoting virus growth, but its role in hPIV2 replication and transcription is not clear. A green fluorescent protein (GFP)-expressing a negative-sense minigenomic construct of hPIV2 has been established by standard technology, with helper plasmids expressing the nucleocapsid protein (NP), phosphoprotein (P), and large RNA polymerase (L) protein, to examine the role of V protein. We found that the simultaneous expression of wild-type V protein in the minigenome system inhibited GFP expression, at least in part, by inhibiting minigenome replication. In contrast, expression of C terminally truncated or mutant hPIV2 V proteins had no effect. Moreover, the V protein of simian virus 41, the rubulavirus most closely related virus to hPIV2, also inhibited GFP expression, whereas that of PIV5, a more distantly related rubulavirus, did not. Using these other rubulavirus V proteins, as well as various mutant hPIV2 V proteins, we found that the ability of V protein to inhibit GFP expression correlated with its ability to bind to L protein via its C-terminal V protein-specific region, but there was no correlation with NP binding. A possible role for this inhibition of genome replication in promoting viral fitness is discussed.Human parainfluenza virus type 2 (hPIV2) is a member of the Rubulavirus genus of the family Paramyxoviridae. This family includes many well-known human and animal pathogens, such as Sendai virus (SeV), hPIV types 1 to 4, simian virus 41 (SV41), parainfluenza virus type 5 (PIV5; formerly known as SV5), mumps virus, Newcastle disease virus, measles virus (MeV), and respiratory syncytial virus, as well as important emerging viruses such as Hendra and Nipah viruses. The negative-stranded RNA genome of hPIV2 is 15,654 nucleotides long and encodes seven viral proteins from six genes (30). The nucleocapsid protein (NP), phosphoprotein (P), and large RNA polymerase (L) protein are important for transcription and replication of the viral RNA genome. All viruses of the Paramyxoviridae (with the notable exception of hPIV1) contain an mRNA-editing site at which G residues are inserted into the P gene mRNA in a programmed manner during its synthesis. In respiroviruses and morbilliviruses, the P mRNA is a faithful copy of the genome RNA, and the V mRNA results from the insertion of one additional pseudotemplated G nucleotide. In only rubulaviruses, it is the V mRNA that is a faithful transcript of the V/P gene, whereas the P mRNA is synthesized through a cotranscriptional insertion of two pseudotemplated G residues. Thus, the N-terminal 164 amino acids (aa) of the V and P proteins are common, while their C termini are unique (43). Since insertion of the G residues in hPIV2 occurs ca. 50% of the time, roughly equal amounts of V and P mRNAs are produced. The C termini of the V proteins contain seven invariant cysteines that bind two atoms of zinc and is ca. 50% identical in sequence among all par...

“…AKT phosphorylates the P protein of PIV5 to upregulate its gene expression whereas PLK1's phosphorylation of P of PIV5 downregulates its gene expression. It has been proposed to target host kinases that are critical for viral RNA synthesis as an antiviral strategy for these paramyxoviruses (25). The identification of S/T residues and phosphorylation sites within MuV P will aid in the identification of host kinases that are important for MuV replication, which will lead to novel targets for anti-MuV drug development.…”

Section: Discussionmentioning

confidence: 99%

Roles of Serine and Threonine Residues of Mumps Virus P Protein in Viral Transcription and Replication

Pickar

Elson

et al. 2014

Self Cite

Mumps virus (MuV), a paramyxovirus containing a negative-sense nonsegmented RNA genome, is a human pathogen that causes an acute infection with symptoms ranging from parotitis to mild meningitis and severe encephalitis. Vaccination against mumps virus has been effective in reducing mumps cases. However, recently large outbreaks have occurred in vaccinated populations. There is no anti-MuV drug. Understanding replication of MuV may lead to novel antiviral strategies. MuV RNA-dependent RNA polymerase minimally consists of the phosphoprotein (P) and the large protein (L). The P protein is heavily phosphorylated. To investigate the roles of serine (S) and threonine (T) residues of P in viral RNA transcription and replication, P was subjected to mass spectrometry and mutational analysis. P, a 392-amino acid residue protein, has 64 S and T residues. We have found that mutating nine S/T residues significantly reduced and mutating residue T at 101 to A (T101A) significantly enhanced activity in a minigenome system. A recombinant virus containing the P-T101A mutation (rMuV-P-T101A) was recovered and analyzed. rMuV-P-T101A grew to higher titers and had increased protein expression at early time points. Together, these results suggest that phosphorylation of MuV-P-T101 plays a negative role in viral RNA synthesis. This is the first time that the P protein of a paramyxovirus has been systematically analyzed for S/T residues that are critical for viral RNA synthesis. IMPORTANCE Mumps virus (MuV) is a reemerging paramyxovirus that caused large outbreaks in the UnitedStates, where vaccination coverage is very high. There is no anti-MuV drug. In this work, we have systematically analyzed roles of Ser/Thr residues of MuV P in viral RNA synthesis. We have identified S/T residues of P critical for MuV RNA synthesis and phosphorylation sites that are important for viral RNA synthesis. This work leads to a better understanding of viral RNA synthesis as well as to potential novel strategies to control mumps. Mumps virus (MuV) is a human pathogen that causes acute parotitis and is highly neurotropic (1). Invasion of the central nervous system is evident in almost half of all clinical cases, with asceptic meningitis occurring in approximately 10% of cases and encephalitis in less than 1% (1). Even though the mumps vaccine has dramatically reduced disease incidence, large outbreaks have recently occurred in vaccinated populations (2, 3). Over 5,700 mumps cases were reported in a 2006 outbreak that originated at a university in Iowa and spread to 10 other states (2). A mumps outbreak occurred in New York and New Jersey in 2009 to 2010 where 88% of the patients had one dose of mumps vaccine and 75% of patients had two doses (3). There is no antiviral drug for MuV infection. Understanding functions of viral proteins will aid development of antiviral strategies. In this study, a strain of MuV from a recent outbreak in Iowa in 2006 (4), MuV Iowa/US/06 (referred to here as MuV), was used to examine the role of phosphorylation of the M...