Manipulation of the N‐terminal sequence of the Borna disease virus X protein improves its mitochondrial targeting and neuroprotective potential

• Published in: The FASEB journal 2016-04, Vol.30 (4), p.1523-1533
• Main Authors: Ferré, Cécile A., Davezac, Noelie, Thouard, Anne, Peyrin, Jean‐Michel, Belenguer, Pascale, Miquel, Marie‐Christine, Gonzalez‐Dunia, Daniel, Szelechowski, Marion
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Aspartic Acid - genetics; Aspartic Acid - metabolism; Axons - drug effects; Axons - metabolism; Blotting, Western; Borna disease virus - genetics; Borna disease virus - metabolism; Cells, Cultured; Cercopithecus aethiops; COS Cells; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; HEK293 Cells; Humans; Life Sciences; Microscopy, Fluorescence; Mitochondria - metabolism; Molecular Sequence Data; Mutation; Neurons - cytology; Neurons - drug effects; Neurons - metabolism; Neurons and Cognition; neuroprotection; nuclear export; Nuclear Localization Signals - genetics; Sequence Homology, Amino Acid; subcellular addressing; Viral Proteins - genetics; Viral Proteins - metabolism
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fj.15-279620

To favor their replication, viruses express proteins that target diverse mammalian cellular pathways. Due to the limited size of many viral genomes, such proteins are endowed with multiple functions, which require targeting to different subcellular compartments. One salient example is the X protein of Borna disease virus, which is expressed both at the mitochondria and in the nucleus. Moreover, we recently demonstrated that mitochondrial X protein is neuroprotective. In this study, we sought to examine the mechanisms whereby the X protein transits between subcellular compartments and to define its localization signals, to enhance its mitochondrial accumulation and thus, potentially, its neuroprotective activity. We transfected plasmids expressing fusion proteins bearing different domains of X fused to enhanced green fluorescent protein (eGFP) and compared their subcellular localization to that of eGFP. We observed that the 5–16 domain of X was responsible for both nuclear export and mitochondrial targeting and identified critical residues for mitochondrial localization. We next took advantage of these findings and constructed mutant X proteins that were targeted only to the mitochondria. Such mutants exhibited enhanced neuroprotective properties in compartmented cultures of neurons grown in microfluidic chambers, thereby confirming the parallel between mitochondrial accumulation of the X protein and its neuroprotective potential.—Ferré C. A., Davezac, N., Thouard, A., Peyrin, J. M., Belenguer, P., Miquel, M.‐C., Gonzalez‐Dunia, D., Szelechowski, M. Manipulation of the N‐terminal sequence of the Borna disease virus X protein improves its mitochondrial targeting and neuroprotective potential. FASEB J. 30, 1523–1533 (2016). www.fasebj.org