Cooperativity of actin and microtubule elements during replication of respiratory syncytial virus

Abstract

Many paramyxoviruses appear to require cytoskeletal elements for particular steps in the virus life cycle. Measles virus and Sendai virus exhibit a requirement for microtubules in replication in vitro, whereas parainfluenza virus type 3 and RSV require actin for replication. To further elucidate the role of cytoskeletal function and rearrangement in the viral life cycle of RSV, we investigated the efficiency of virus entry, transcription, replication, and budding in the presence of a variety of pharmacological agents that stabilize or depolymerize actin or microtubules. We found that alteration of microtubule or actin function resulted in blocks at entry, formation of cell-associated virus, virus release, local cell-to-cell spread, and syncytium formation. Actin and microtubules act in cooperation to facilitate replication of RSV, although microtubules play a dominant role in the formation of cell-associated virus while actin plays a more prominent role in virus release.

The Human Respiratory Syncytial Virus Matrix Protein Is Required for Maturation of Viral Filaments

“…However, the role of polymerized actin seems to be limited to the actual budding/release event (11,30,32), which was shown previously to occur at sites of lipid rafts (8,9,22,27,31,36,42,49,50). In contrast to polymerized actin, microtubules were reported previously to be involved in virus production at a step prior to budding (32). Although the role of cytoskeletal components in RNP transport are far from understood, our data implicate the M protein in this process.…”

“…Several cytoskeletal proteins, including actin isoforms, cofilin, and filamin-1, were detected by mass spectrometry analyses of purified viral filaments (although purity was difficult to assess due to the cell-associated nature of filaments). There is ample evidence of a role for polymerized actin and actinregulatory proteins in assembly (4,6,11,22,30,32,49,53,59). However, the role of polymerized actin seems to be limited to the actual budding/release event (11,30,32), which was shown previously to occur at sites of lipid rafts (8,9,22,27,31,36,42,49,50).…”

“…However, the composition and functions of IBs, including a potential role in viral filament formation, are poorly understood. Several reports have implicated cytoskeletal elements in the processes that lead to virus egress, in particular microtubules, myosin V, actin, and actin-regulatory proteins such as profilin and RhoA (30,32,59). In addition, a role for an actin/myosinbased motility system in HRSV exit has been proposed (6,53,59), and there is strong evidence for the involvement of lipid rafts (8,9,22,27,31,36,49,50,53).…”

Entry of Feline Calicivirus Is Dependent on Clathrin-Mediated Endocytosis and Acidification in Endosomes

“…This is the first report of cytochalasin D inhibiting the replication of a nonenveloped RNA virus. There are examples of the importance of an intact actin network in the transcription/ replication of human parainfluenza virus type 3, canine distemper virus, respiratory syncytial virus, and Newcastle disease virus (8,12,13,14,23,24,29,30). Early ultrastructural studies of FCV infection noted the formation of filaments in infected cells and the association of virions with these filaments (33).…”

Integrin αvβ1 promotes infection by human metapneumovirus

“…In fact, we detected an increase in RSV-infected cells following treatment with integrin-specific siRNAs. We speculate that this effect is attributable to altered cell morphology or cytoskeletal rearrangements that serve to promote RSV infection (37). Therefore, reducing cell-surface expression of ␣v and ␤1 integrins reduces the efficiency of hMPV infection.…”