Nuclear Heat Shock Response and Novel Nuclear Domain 10 Reorganization in Respiratory Syncytial Virus-Infected A549 Cells Identified by High-Resolution Two-Dimensional Gel Electrophoresis

The pneumovirus respiratory syncytial virus (RSV) is a leading cause of epidemic respiratory tract infection. Upon entry, RSV replicates in the epithelial cytoplasm, initiating compensatory changes in cellular gene expression. In this study, we have investigated RSV-induced changes in the nuclear proteome of A549 alveolar type II-like epithelial cells by high-resolution two-dimensional gel electrophoresis (2DE). Replicate 2D gels from uninfected and RSV-infected nuclei were compared for changes in protein expression. We identified 24 different proteins by peptide mass fingerprinting after matrix-assisted laser desorption ionization-time of flight mass spectrometry (MS), whose average normalized spot intensity was statistically significant and differed by ±2-fold. Notable among the proteins identified were the cytoskeletal cytokeratins, RNA helicases, oxidant-antioxidant enzymes, the TAR DNA binding protein (a protein that associates with nuclear domain 10 [ND10] structures), and heat shock protein 70- and 60-kDa isoforms (Hsp70 and Hsp60, respectively). The identification of Hsp70 was also validated by liquid chromatography quadropole-TOF tandem MS (LC-MS/MS). Separate experiments using immunofluorescence microscopy revealed that RSV induced cytoplasmic Hsp70 aggregation and nuclear accumulation. Data mining of a genomic database showed that RSV replication induced coordinate changes in Hsp family proteins, including the 70, 70-2, 90, 40, and 40-3 isoforms. Because the TAR DNA binding protein associates with ND10s, we examined the effect of RSV infection on ND10 organization. RSV induced a striking dissolution of ND10 structures with redistribution of the component promyelocytic leukemia (PML) and speckled 100-kDa (Sp100) proteins into the cytoplasm, as well as inducing their synthesis. Our findings suggest that cytoplasmic RSV replication induces a nuclear heat shock response, causes ND10 disruption, and redistributes PML and Sp100 to the cytoplasm. Thus, a high-resolution proteomics approach, combined with immunofluorescence localization and coupled with genomic response data, yielded unexpected novel insights into compensatory nuclear responses to RSV infection.