Mitochondrial proteomic analysis of human host cells infected with H3N2 swine influenza virus.

Swine influenza viruses (SIV) are zoonotic pathogens that pose a potential threat to human health. In this study, we analyzed the differential mitochondrial proteomes of H3N2 SIV-infected human lung A549 cells using two-dimensional gel electrophoresis (2-DE) followed by matrix-assisted laser desorption ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) analysis. In the comparative analysis, 24 altered proteins (13 upregulated and 11 downregulated) were identified in the mitochondria of H3N2 SIV-infected cells; these proteins were involved in cell-to-cell signaling and interaction, cellular movement, and post-translational modification. Moreover, the transcriptional profiles of 16 genes corresponding to the identified proteins were estimated by real time RT-PCR. IPA analysis suggested that the differentially expressed proteins were clustered primarily into the mammalian target of rapamycin (mTOR) and d-glucose signaling pathways. In addition, oxidative phosphorylation and integrin signaling appeared to be major pathways modulated in the mitochondria of infected cells. We further demonstrated that apolipoprotein L2 was upregulated in the cytoplasm and translocated to mitochondria during virus infection. These results were verified by Western blot analysis coupled with confocal microscopy. Collectively, the mitochondrial proteome data provide insights to further understand the underlying mechanisms of H3N2 SIV cross-species infection. BIOLOGICAL SIGNIFICANCE: In recent years, proteomics has emerged as an indispensable tool to unveil the complex molecular events in virology. we firstly perform mitochondrial proteomic profiles of human cells infected with H3N2 subtype SIV to understand virus-host interactions, and 24 differentially expressed proteins in mitochondrial proteomes were identified in SIV-infected cells. The proteins that were identified to have differential expression were involved in cell-to-cell signaling and interaction, post-translational modification, cell morphology, cellular assembly, cell death, and energy production. Furthermore, Western blot analysis and a confocal assay further demonstrated that the cellular protein APOL2 partially co-localized with mitochondria after virus infection. This is a very important discovery in the underlying replication and pathogenesis of SIV which provides a potential target clue for the design of anti-SIV drugs. Our results will inspire basic study on SIV infection and drive the understanding for replication and pathogenesis of SIV to control this disease.