The polyomavirus BK agnoprotein co-localizes with lipid droplets

• Published in: Virology (New York, N.Y.) Vol. 399; no. 2; pp. 322 - 331
• Main Authors: Unterstab, Gunhild, Gosert, Rainer, Leuenberger, David, Lorentz, Pascal, Rinaldo, Christine H, Hirsch, Hans H
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 10.04.2010
• Subjects: 60 APPLIED LIFE SCIENCES; Accessory protein; Agnoprotein; ALANINES; Amino Acid Sequence; AMINO ACIDS; Animals; ASPARTIC ACID; BK virus; BK Virus - chemistry; BODY; CARBOXYLIC ACIDS; Cell Nucleus - chemistry; Cells, Cultured; Cercopithecus aethiops; CHEMICAL REACTIONS; CLSM; Cytoplasm - chemistry; Deconvolution; DROPLETS; Humans; HYDROXY ACIDS; Infection; Infectious Disease; KIDNEYS; Lipid droplets; LIPIDS; Lipids - chemistry; MICROORGANISMS; Microscopy, Confocal; Microscopy, Fluorescence; Molecular Sequence Data; Mutation; MUTATIONS; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANS; PARASITES; PARTICLES; PHOSPHORYLATION; Polyomavirus; Protein Structure, Secondary; PROTEINS; SERINE; Transfection; Vero Cells; Viral Regulatory and Accessory Proteins - chemistry; VIRUSES; Agnoprotein; Infection; Deconvolution; Transfection; Lipid droplets; Polyomavirus; BK virus; Accessory protein; CLSM
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/j.virol.2010.01.011

Abstract Agnoprotein encoded by human polyomavirus BK (BKV) is a late cytoplasmic protein of 66 amino acids (aa) of unknown function. Immunofluorescence microscopy revealed a fine granular and a vesicular distribution in donut-like structures. Using BKV(Dunlop)-infected or agnoprotein-transfected cells, we investigated agnoprotein co-localization with subcellular structures. We found that agnoprotein co-localizes with lipid droplets (LD) in primary human renal tubular epithelial cells as well as in other cells supporting BKV replication in vitro (UTA, Vero cells). Using agnoprotein-enhanced green fluorescent protein (EGFP) fusion constructs, we demonstrate that agnoprotein aa 20–42 are required for targeting LD, whereas aa 1–20 or aa 42–66 were not. Agnoprotein aa 22–40 are predicted to form an amphipathic helix, and mutations A25D and F39E, disrupting its hydrophobic domain, prevented LD targeting. However, changing the phosphorylation site serine-11 to alanine or aspartic acid did not alter LD co-localization. Our findings provide new clues to unravel agnoprotein function.