The polyomavirus BK agnoprotein co-localizes with lipid droplets.
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.
Transplantation Virology, Institute for Medical Microbiology, Department of Biomedicine, University of Basel, CH-4003 Basel, Switzerland.
Gunhild
G
Unterstab
Rainer
R
Gosert
David
D
Leuenberger
Pascal
P
Lorentz
Christine H
CH
Rinaldo
Hans H
HH
Hirsch
D000595:Amino Acid Sequence; D000818:Animals; D001739:BK Virus / Q000737:chemistry*; D002467:Cell Nucleus / Q000737:chemistry; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000737:chemistry; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D017433:Protein Structure, Secondary; D014709:Vero Cells; D054334:Viral Regulatory and Accessory Proteins / Q000737:chemistry*; D000086082:Viroporin Proteins
D008055:Lipids; D054334:Viral Regulatory and Accessory Proteins; C042559:agnoprotein, polyomavirus; D000086082:Viroporin Proteins