Abstract
The autonomous parvovirus Minute Virus of Mice (MVM) induces specific changes in the cytoskeleton filaments of infected permissive cells, causing in particular the degradation of actin fibers and the generation of “actin patches.” This is attributed to a virus-induced imbalance between the polymerization factor N-WASP (Wiscott-Aldrich syndrome protein) and gelsolin, a multifunctional protein cleaving actin filaments. Here, the focus is on the involvement of gelsolin in parvovirus propagation and virus-induced actin processing. Gelsolin activity was knocked-down, and consequences thereof were determined for virus replication and egress and for actin network integrity. Though not required for virus replication or progeny particle assembly, gelsolin was found to control MVM (and related H1-PV) transport from the nucleus to the cell periphery and release into the culture medium. Gelsolin-dependent actin degradation and progeny virus release were both controlled by (NS1)/CKIIα, a recently identified complex between a cellular protein kinase and a MVM non-structural protein. Furthermore, the export of newly synthesized virions through the cytoplasm appeared to be mediated by (virus-modified) lysomal/late endosomal vesicles. By showing that MVM release, like entry, is guided by the cytoskeleton and mediated by vesicles, these results challenge the current view that egress of non-enveloped lytic viruses is a passive process.
Highlights
The genus parvovirus (PV) consists of small icosahedral nonenveloped particles with a 5.1-kb linear single-stranded DNA genome
Egress of non-enveloped lytic viruses is commonly thought to occur as a virus burst after cell disintegration
We showed in the past that autonomous parvoviruses induce severe cytopathic effects to the host cell, manifested in restructuring and degradation of cytoskeletal filaments, thereby supporting such mode of virus spread
Summary
The genus parvovirus (PV) consists of small icosahedral nonenveloped particles with a 5.1-kb linear single-stranded DNA genome. In addition to its direct involvement in particle production, NS1 acts to jeopardize the integrity and survival of infected cells [4,5,6]. It has been shown to control the activity and properties of selected cell components through physical interaction [7,8] and/or induction of post-translational modifications [9,10]. Such targets might be modified either directly by NS1/CKIIa, a recently described complex formed by NS1 with the catalytic domain of cellular CKII [8], or indirectly through activation/ modulation of the PDK-1/PKC signaling cascade [11]
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