Ezrin-Radixin-Moesin Family Proteins Are Involved in Parvovirus Replication and Spreading

Abstract

The propagation of autonomous parvoviruses is strongly dependent on the phosphorylation of the major nonstructural protein NS1 by members of the protein kinase C (PKC) family. Minute virus of mice (MVM) replication is accompanied by changes in the overall phosphorylation pattern of NS1, which is newly modified at consensus PKC sites. These changes result, at least in part, from the ability of MVM to modulate the PDK-1/PKC pathway, leading to activation and redistribution of both PDK-1 and PKC . We show that proteins of the ezrin-radixin-moesin (ERM) family are essential for virus propagation and spreading through their functions as adaptors for PKC . MVM infection led to redistribution of radixin and moesin in the cell, resulting in increased colocalization of these proteins with PKC . Radixin was found to control the PKCdriven phosphorylation of NS1 and newly synthesized capsids in vivo. Conversely, radixin phosphorylation and activation were driven by the NS1/CKII␣ complex. Altogether, these data argue for ERM proteins being both targets and modulators of parvovirus infection.

Vesicular Transport of Progeny Parvovirus Particles through ER and Golgi Regulates Maturation and Cytolysis

“…This is mainly attributed to the large nonstructural viral protein NS1, a multifunctional protein involved in particle production and spread (reviewed in [35]). NS1 was shown to modulate cellular pathways by physical interactions with distinct cell components [36,37] and/or induction of post-translational modifications of cellular target proteins [3,20,37,38]. These targets might be modified either directly by NS1/CKIIa, a recently described complex formed by NS1 with the catalytic domain of cellular CKII [36], or indirectly through activation/modulation of the PDK1/PKC/PKB signaling cascade [39].…”

An In-Frame Deletion in the NS Protein-Coding Sequence of Parvovirus H-1PV Efficiently Stimulates Export and Infectivity of Progeny Virions

“…The shortened nonstructural proteins delNS1 and delNS2 are good candidates for viral effectors involved in the improved fitness of Del H-1PV. Indeed, the in-frame deletion in the Del H-1PV genome results in the alteration of the primary structure of both viral proteins by removing 38 amino acids from their sequences and may thus interfere with their known functioning in the production and intracellular trafficking of progeny virions (1,21,38).…”

“…NS1 is a multifunctional, mainly nuclear, phosphorylated protein of about 83 kDa that is required for the replication of the viral genome, in particular, due to its helicase, endonuclease, ATPase, and site-specific DNAbinding activities (15,30). Besides its function in viral DNA replication, NS1 transactivates the P38 promoter (10,20,30), plays a critical role in the vesicular egress of progeny virions (1,38), and is the main determinant of parvoviral cytotoxicity (30,39). Like NS1, the small NS2 proteins (about 25 kDa) are essential for various steps of the parvovirus life cycle, but unlike NS1, they do not appear to display any enzymatic activity.…”

“…However, besides a greater accumulation of NS2-encoding R2 transcripts and higher levels of neosynthesized NS2 proteins, no significant differences between H-1 dr and H-1 standard viruses were detected with regard to their ability to produce viral DNA replicative forms (RFs), progeny single-stranded DNA, or capsids (23). Both nonstructural proteins are also known to play key roles at late steps of the virus life cycle, such as the formation of progeny viral particles and their intracellular trafficking from the nucleus to the plasma membrane of infected cells (1,12,38). This prompted us to further analyze the effects of the above-mentioned in-frame deletion within the nonstructural genes on the production and egress of progeny virus in the absence of the sequence duplication found in the right-hand hairpin of the H-1 dr genome.…”

Late Maturation Steps Preceding Selective Nuclear Export and Egress of Progeny Parvovirus

“…Accordingly, dramatic retention of virions in the perinuclear area and inhibition of virion release into the medium were observed in cells lacking functional effectors of the secretory pathway (13). In addition, members of the ezrin-radixin-moesin (ERM) family have been shown to play a role in virus maturation and spreading capacity, as judged by their impact on MVM plaque morphology (26). Dominant negative radixin or moesin mutants failed to wrap progeny virions into transport vesicles, resulting in a marked reduction in virus egress.…”