Arenavirus nucleoprotein localizes to mitochondria

Abstract

Viruses need cells to replicate and, therefore, ways to counteract the host's immune response. Mitochondria play central roles in mediating innate immunity, hence some viruses have developed mechanisms to alter mitochondrial functions. Herein we show that arenavirus nucleoprotein (NP) enters the mitochondria of infected cells and affects their morphological integrity. We initially demonstrate electron-dense inclusions within mitochondria of reptarenavirus infected cells and hypothesized that these represent viral NP. Software predictions then serve to identify a putative N-terminal mitochondrial targeting signal (MTS) in arenavirus NPs; however, comparisons of wild-type and N-terminus mutated NPs suggest MTS-independent mitochondrial entry. NP does not enter isolated mitochondria, indicating that translocation requires additional cellular factors or conditions. Immune electron microscopy finally confirms the presence of NP within the mitochondria both in vitro and in infected animals. We hypothesize that mitochondria targeting might complement the known interferon antagonist functions of NP or alter the cell's metabolic state.

Persistent Reptarenavirus and Hartmanivirus Infection in Cultured Boid Cells

“…However, although not apparent from the present confocal images, most of the persistently infected cells appeared to stain weakly for reptarenavirus NP, as supported by the immunoblot and qRT-PCR results. Different from the granular/punctate reptarenavirus NP expression in the cells, hartmanivirus NP appeared diffusely distributed in the cytoplasm of infected cells, as observed in earlier studies ( 6 , 23 ).…”

“…We have generated several rabbit antisera against the NPs of reptarena- ( 1 , 20 , 22 ) and hartmaniviruses ( 6 , 23 ), which in the case of reptarenaviruses, but not hartmaniviruses show good cross-reactivity between NPs of different species. Somewhat surprisingly, GP2 appears to be the most conserved reptarenaviral protein because the GP2s of different reptarenavirus species (excluding the California Academy of Sciences virus [CASV]) show amino acid identities between 87 and 99% ( 6 ).…”

Boid Inclusion Body Disease Is Also a Disease of Wild Boa Constrictors

“…For the preparation of cell pellets from the inoculated cell cultures, cells were trypsinised (trypsin 10×; Merck Biochrome) for 5 min at room temperature and then spun at 1,000× RCF for 3 min. The resulting pellet was either fixed in 4% buffered paraformaldehyde overnight and routinely embedded in paraffin wax for histology and immunohistology or was fixed in 2.5% phosphate-buffered glutaraldehyde and embedded in epoxy resin for transmission electron microscopy using routine methods, as described previously ( 26 , 40 ).…”

Boid Inclusion Body Disease (BIBD) Is Also a Disease of Wild Boa Constrictors

“…For the preparation of cell pellets from the inoculated cell cultures, cells were trypsinised (Trypsin 10x, Merck Biochrome) for 5 min at room temperature, then spun at 1,000 x RCF for 3 min. The resulting pellet was either fixed in 4% buffered paraformaldehyde overnight and routinely embedded in paraffin wax for histology and immunohistology, or was fixed in 2.5% phosphate buffered glutaraldehyde and routinely epoxy resin embedded for transmission electron microscopy, as previously described (24, 31).…”

“…The resulting pellet was either fixed in 4% buffered paraformaldehyde overnight and routinely embedded in paraffin wax for histology and immunohistology, or was fixed in 2.5% phosphate buffered glutaraldehyde and routinely epoxy resin embedded for transmission electron microscopy, as previously described (24,31).…”