Transplantation Virology, Institute for Medical Microbiology, Department of Biomedicine, University of Basel, CH-4003 Basel, Switzerland.
Virology. 2010 Apr 10;399(2):322-31. doi: 10.1016/j.virol.2010.01.011.
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.
人多瘤病毒 BK（BKV）编码的 Agnoprotein 是一种未知功能的 66 个氨基酸（aa）的晚期细胞质蛋白。免疫荧光显微镜显示呈类甜甜圈样结构的细颗粒状和囊泡状分布。使用 BKV（Dunlop）感染或 Agnoprotein 转染的细胞，我们研究了 Agnoprotein 与亚细胞结构的共定位。我们发现，Agnoprotein 与人原代肾小管上皮细胞中的脂滴（LD）以及体外支持 BKV 复制的其他细胞（UTA、Vero 细胞）共定位。使用 Agnoprotein-增强型绿色荧光蛋白（EGFP）融合构建体，我们证明了 Agnoprotein aa 20-42 是靶向 LD 所必需的，而 aa 1-20 或 aa 42-66 则不是。Agnoprotein aa 22-40 预测形成一个两亲性螺旋，破坏其疏水区的突变 A25D 和 F39E 阻止了 LD 靶向。然而，将磷酸化位点丝氨酸-11 改变为丙氨酸或天冬氨酸并没有改变 LD 的共定位。我们的发现为揭示 Agnoprotein 功能提供了新的线索。
