Actin-Modulating Protein Cofilin Is Involved in the Formation of Measles Virus Ribonucleoprotein Complex at the Perinuclear Region

Abstract

In measles virus (MV)-infected cells, the ribonucleoprotein (RNP) complex, comprised of the viral genome and the nucleocapsid (N) protein, phosphoprotein (P protein), and large protein, assembles at the perinuclear region and synthesizes viral RNAs. The cellular proteins involved in the formation of the RNP complex are largely unknown. In this report, we show that cofilin, an actin-modulating host protein, interacts with the MV N protein and aids in the formation of the RNP complex. Knockdown of cofilin using the short hairpin RNA reduces the formation of the RNP complex after MV infection and that of the RNP complex-like structure after plasmid-mediated expression of MV N and P proteins. A lower level of formation of the RNP complex results in the reduction of viral RNA synthesis. Cofilin phosphorylation on the serine residue at position 3, an enzymatically inactive form, is increased after MV infection and the phosphorylated form of cofilin is preferentially included in the complex. These results indicate that cofilin plays an important role in MV replication by increasing formation of the RNP complex and viral RNA synthesis. IMPORTANCE Many Measles is a highly contagious viral disease characterized by high fever, respiratory symptoms, conjunctivitis, and a macropapular rash. The patients exhibit immunosuppression, often resulting in secondary infections, the main cause of measles-associated mortality and morbidity. On rare occasions, measles virus (MV) persists in the central nervous system and causes subacute sclerosing panencephalitis with long incubation periods (1). Although mortality and morbidity have been greatly reduced thanks to worldwide vaccination efforts, the World Health Organization estimates that 145,700 people died of measles in 2013 (http://www .who.int/mediacentre/factsheets/fs286/en/).MV, a member of the genus Morbillivirus in the family Paramyxoviridae, possesses 6 genes coding for the nucleocapsid (N) protein, phosphoprotein (P protein), matrix (M) protein, and hemagglutinin (HA), fusion, and large proteins. The two envelope glycoproteins, the hemagglutinin and fusion proteins, mediate receptor binding and membrane fusion, respectively (1). Pathogenic MVs use as cellular receptors the signaling lymphocyte activation molecule (SLAM) (2, 3) and nectin 4 (4, 5), which are expressed on immune and epithelial cells, respectively. The N, P, and large proteins, together with the viral genome, constitute the ribonucleoprotein (RNP) complex, which is found at the perinuclear region in MV-infected cells (6-8) and functions as the RNAdependent RNA polymerase. The M protein is involved in virion assembly and the budding process (1).Besides the P protein, the MV P gene encodes two additional proteins, C and V (9, 10). The V mRNA is produced through the insertion of a single nontemplated guanine at the editing site of the P gene during the transcription. The V protein possesses 231 amino acid residues in the N terminus which are identical to those possessed by the P protein and 68 unique resid...

Porcine Hemagglutinating Encephalomyelitis Virus Activation of the Integrin α5β1-FAK-Cofilin Pathway Causes Cytoskeletal Rearrangement To Promote Its Invasion of N2a Cells

“…PAK is an evolutionarily conserved serine/threonine protein kinase whose phosphorylation promotes the formation of actin filaments through the inactivation of cofilin; the dephosphorylation restores the interaction between cofilin molecules and actin monomers, which depolymerizes actin filaments. This regulatory process affects the rearrangement of the actin cytoskeleton ( 6 ). Although both Rac1 and Cdc42 regulated the actin cytoskeleton rearrangement through PAK, we found that the activation time of Rac1 and Cdc42 in PHEV invasion of N2a cells was different.…”

“…Although a virus does not contain a cytoskeletal system, viruses utilize the cytoskeleton system of a host cell to complete the infection process ( 2 , 3 ). Currently, numerous experiments show that the actin cytoskeleton is crucial for many stages of the viral life cycle, including binding, entry, nuclear localization, genomic transcription and reverse transcription, assembly, and export/dissemination ( 4 – 6 ). Porcine hemagglutinating encephalomyelitis virus (PHEV), a member of the Coronaviridae family, is a highly neurovirulent virus that spreads to the central nervous system via peripheral nerves ( 7 ).…”

Negri bodies and other virus membrane-less replication compartments

“…Another heat shock protein (Hsp72) is found associated with MuV IBs [ 26 ]. The WD repeat-containing protein 5 (WDR5), a subunit of histone H3 lysine 4 methyltransferase, as well as the actin-modulating protein cofilin [ 97 , 98 ] concentrate in MeV ones. The phosphorylated mitogen-activated protein kinase p38, a key regulator of cellular inflammatory and stress responses, and the O-linked N -acetylglucosamine (OGN) transferase, an enzyme that catalyzes the posttranslational addition of OGN to protein and is also involved in stress response, are sequestered in RSV IBs [ 99 ].…”

Measles Virus Forms Inclusion Bodies with Properties of Liquid Organelles

“…Although IBs are believed to represent major sites of viral transcription and replication of Mononegavirales, how IBs are formed and regulated is little understood. Even though we and others have identified host proteins localized to IBs (28)(29)(30), including the WD repeat-containing protein 5 (WDR5) (16), the identity and function of IB-associated host factors largely remain unknown. A technical hurdle is that the isolation and purification of IBs have proven challenging, partially due to the lack of a membrane separating IBs from other cytoplasmic constituents.…”