Interactions of viral matrix protein and nucleoprotein with the host cell cytoskeletal actin in influenza viral infection

Abstract

To understand the role of host cell cytoskeleton in regulating the assembly and budding of the externally enveloped viruses, we have studied the interactions between the cytoskeleton and viral proteins in the influenza A virus-infected Madin-Darby canine kidney (MDCK) cells, employing immunofluorescence microscopy and biochemical techniques. The Triton X-100-insoluble cytoskeletons prepared from the infected cells contained at least two viral proteins, viz. matrix protein (MP) and nucleoprotein (NP), the quantities of which considerably reduced (at least by 60%) upon including 1 M sodium chloride or 2.5 M urea in Triton X-100 (2%). Also, an extraction of these cytoskeletons in presence of the reagents that solubilized the cytoskeletal actin resulted in a release of actin together with NP and MP. Besides, these viral proteins were observed to codistribute with actin in both the cytochalasin E-treated and untreated infected cells. These results demonstrate that NP and MP ionically interact with cytoskeletal actin in the influenza virus-infected MDCK cells.