Murine Coronavirus Replication-Induced p38 Mitogen-Activated Protein Kinase Activation Promotes Interleukin-6 Production and Virus Replication in Cultured Cells

Abstract

Analyses of mitogen-activated protein kinases (MAPKs) in a mouse hepatitis virus (MHV)-infected macrophage-derived J774.1 cell line showed activation of two MAPKs, p38 MAPK and c-Jun N-terminal kinase (JNK), but not of extracellular signal-regulated kinase (ERK). Activation of MAPKs was evident by 6 h postinfection. However, UV-irradiated MHV failed to activate MAPKs, which demonstrated that MHV replication was necessary for their activation. Several other MHV-permissive cell lines also showed activation of both p38 MAPK and JNK, which indicated that the MHV-induced stress-kinase activation was not restricted to any particular cell type. The upstream kinase responsible for activating MHV-induced p38 MAPK was the MAPK kinase 3. Experiments with a specific inhibitor of p38 MAPK, SB 203580, demonstrated that MHVinduced p38 MAPK activation resulted in the accumulation of interleukin-6 (IL-6) mRNAs and an increase in the production of IL-6, regardless of MHV-induced general host protein synthesis inhibition. Furthermore, MHV production was suppressed in SB 203580-treated cells, demonstrating that activated p38 MAPK played a role in MHV replication. The reduced MHV production in SB 203580-treated cells was, at least in part, due to a decrease in virus-specific protein synthesis and virus-specific mRNA accumulation. Interestingly, there was a transient increase in the amount of phosphorylation of the translation initiation factor 4E (eIF4E) in infected cells, and this eIF4E phosphorylation was p38 MAPK dependent; it is known that phosphorylated eIF4E enhances translation rates of cap-containing mRNAs. Furthermore, the upstream kinase responsible for eIF4E phosphorylation, MAPK-interacting kinase 1, was also phosphorylated and activated in response to MHV infection. Our data suggested that host cells, in response to MHV replication, activated p38 MAPK, which subsequently phosphorylated eIF4E to efficiently translate certain host proteins, including IL-6, during virus-induced severe host protein synthesis inhibition. MHV utilized this p38 MAPK-dependent increase in eIF4E phosphorylation to promote virus-specific protein synthesis and subsequent progeny virus production. Enhancement of virus-specific protein synthesis through virus-induced eIF4E activation has not been reported in any other viruses.

Cell Entry of Avian Reovirus Follows a Caveolin-1-mediated and Dynamin-2-dependent Endocytic Pathway That Requires Activation of p38 Mitogen-activated Protein Kinase (MAPK) and Src Signaling Pathways as Well as Microtubules and Small GTPase Rab5 Protein

“…An increasing amount of information has demonstrated that many viruses activate the p38 MAPK pathway to augment their efficient replication (51)(52)(53)(54)(55). To this end, although in our earlier study we have demonstrated that p38 MAPK activation is beneficial for ARV replication (31), its precise role in regulating ARV entry and replication remains elusive so far.…”

Hemorrhagic Shock Induces NAD(P)H Oxidase Activation in Neutrophils: Role of HMGB1-TLR4 Signaling

“…The activity of p38 MAPK in PMN was analyzed by using a p38 MAPK assay kit (Cell Signaling Technology) (37). Phosphorylated p38 was immunoprecipitated with a p38-phospho-specific Ab from 200 g of lysate; this Ab specifically recognized phosphorylated p38 and did not cross-react with phosphorylated JNK or ERK1/2.…”

Altered p38 Mitogen-Activated Protein Kinase Expression in Different Leukocytes with Increment of Immunosuppressive Mediators in Patients with Severe Acute Respiratory Syndrome

“…In an attempt to determine whether proinflammatory cytokines or skewed Th (Th1/Th2) cytokines were involved in the pathogenesis of SARS, we collected plasma from SARS patients and controls for measuring proinflammatory cytokines TNF-␣, IL-6, and IL-8, as well as Th reaction mediators IL-2, IL-12, IL-10, TGF-␤, NO, or PGE 2 production. Previous studies with certain viruses including murine coronavirus have shown that inhibition or activation of mitogen-activated protein kinase (MAPK) was involved in induction or suppression of cytokines after virus infection (7,8). We therefore harvested blood leukocytes in 1% formaldehyde for flow cytometric analysis of intracellular MAPK activation, as demonstrated by phospho-p38 and phospho-extracellular signal-regulated kinase (ERK) expression after plasma collection.…”