Actin and RIG-I/MAVS Signaling Components Translocate to Mitochondria upon Influenza A Virus Infection of Human Primary Macrophages

Abstract

Influenza A virus is one of the most important causes of respiratory infection. During viral infection, multiple cell signaling cascades are activated, resulting in the production of antiviral cytokines and initiation of programmed cell death of virus-infected cells. In the present study, we have used subcellular proteomics to reveal the host response to influenza A infection at the protein level in human macrophages. Macrophages were infected with influenza A virus, after which the cytosolic and mitochondrial cell fractions were prepared and analyzed by using two-dimensional electrophoresis for protein separation and mass spectrometry for protein identification. In cytosolic proteomes, the level of several heat shock proteins and fragments of cytoskeletal proteins was clearly up-regulated during influenza A virus infection. In mitochondrial proteomes, simultaneously with the expression of viral proteins, the level of intact actin and tubulin was highly up-regulated. This was followed by translocation of the components of antiviral RNA recognition machinery, including RIG-I (retinoic acid-inducible protein I), TRADD (TNFR1-associated death domain protein), TRIM25 (tripartite motif protein 25), and IKKε (inducible IκB kinase), onto the mitochondria. Cytochalasin D, a potent inhibitor of actin polymerization, clearly inhibited influenza A virus-induced expression of IFN-β, IL-29, and TNF-α, suggesting that intact actin cytoskeleton structure is crucial for proper activation of antiviral response. At late phases of infection mitochondrial fragmentation of actin was seen, indicating that actin fragments, fractins, are involved in disruption of mitochondrial membranes during apoptosis of virus-infected cells. In conclusion, our results suggest that actin network interacts with mitochondria to regulate both antiviral and cell death signals during influenza A virus infection.

Interactions between the Influenza A Virus RNA Polymerase Components and Retinoic Acid-Inducible Gene I

“…5E). In agreement with previous studies (46,55,56), the levels of endo-RIG-I increased significantly in cells infected with either virus (Fig. 5F).…”

“…Enhanced RIG-I expression was observed in A549 cells infected with either wildtype or NS1-deleted WF10 virus (Fig. 5B and F), which corresponds with previous reports regarding upregulated RIG-I expression by influenza virus (46,55,56). In addition, compared with mock-infected cells, both viruses elicited the nuclear import of endo-RIG-I (Fig.…”

HSV-2 Immediate-Early Protein US1 Inhibits IFN-β Production by Suppressing Association of IRF-3 with IFN-β Promoter

“…It binds to dsRNA through the helicase domain and signals through caspase activation and recruitment domains to the adaptor IPS-1. Engagement of RIG-I initiates signaling through two protein kinase complex, TBK-1 and IKK-ε, leading to the phosphorylation and dimerization of IRF-3 (101,102). IRF-3 dimers translocate from the cytoplasm into the nucleus to bind to the IFN-b promoter and to boost IFN-b transcription (16).…”

A mechanism for functional segregation of mitochondrial and cytosolic genetic codes

“…Proper compartmentalization is essential for mitochondrial function, including signaling roles that regulate calcium homeostasis (25), control of apoptosis (26), or viral infection response mechanisms (27). In terms of protein synthesis, however, it is unclear to what extent, if any, does mitochondrial translation need to be separated from cytosolic protein synthesis.…”