White spot syndrome virus protein kinase 1 defeats the host cell's iron-withholding defense mechanism by interacting with host ferritin.
Iron is an essential nutrient for nearly all living organisms, including both hosts and invaders. Proteins such as ferritin regulate the iron levels in a cell, and in the event of a pathogenic invasion, the host can use an iron-withholding mechanism to restrict the availability of this essential nutrient to the invading pathogens. However, pathogens use various strategies to overcome this host defense. In this study, we demonstrated that white spot syndrome virus (WSSV) protein kinase 1 (PK1) interacted with shrimp ferritin in the yeast two-hybrid system. A pulldown assay and 27-MHz quartz crystal microbalance (QCM) analysis confirmed the interaction between PK1 and both ferritin and apoferritin. PK1 did not promote the release of iron ions from ferritin, but it prevented apoferritin from binding ferrous ions. When PK1 was overexpressed in Sf9 cells, the cellular labile iron pool (LIP) levels were elevated significantly. Immunoprecipitation and atomic absorption spectrophotometry (AAS) further showed that the number of iron ions bound by ferritin decreased significantly at 24 h post-WSSV infection. Taken together, these results suggest that PK1 prevents apoferritin from iron loading, and thus stabilizes the cellular LIP levels, and that WSSV uses this novel mechanism to counteract the host cell's iron-withholding defense mechanism.


OBJECTIVE
We show here that white spot syndrome virus (WSSV) ensures the availability of iron by using a previously unreported mechanism to defeat the host cell's iron-withholding defense mechanism. This defense is often implemented by ferritin, which can bind up to 4,500 iron atoms and acts to sequester free iron within the cell. WSSV's novel counterstrategy is mediated by a direct protein-protein interaction between viral protein kinase 1 (PK1) and host ferritin. PK1 interacts with both ferritin and apoferritin, suppresses apoferritin's ability to sequester free iron ions, and maintains the intracellular labile iron pool (LIP), and thus the availability of free iron is increased within cells.
Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan Department of Life Science, College of Life Science, National Taiwan University, Taipei, Taiwan.
Shin-Jen
SJ
Lin
Technology Commons, College of Life Science, National Taiwan University, Taipei, Taiwan.
Der-Yen
DY
Lee
Graduate Institute of Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan.
Hao-Ching
HC
Wang
Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan Department of Life Science, College of Life Science, National Taiwan University, Taipei, Taiwan.
Shih-Ting
ST
Kang
Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan.
Pung-Pung
PP
Hwang
Department of Life Science, College of Life Science, National Taiwan University, Taipei, Taiwan.
Guang-Hsiung
GH
Kou
Graduate Institute of Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan.
Ming-Fen
MF
Huang
Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan gdchang@ntu.edu.tw gracelow@mail.ncku.edu.tw.
Geen-Dong
GD
Chang
Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan Department of Life Science, College of Life Science, National Taiwan University, Taipei, Taiwan gdchang@ntu.edu.tw gracelow@mail.ncku.edu.tw.
Chu-Fang
CF
Lo
D000818:Animals; D002460:Cell Line; D002498:Centrifugation; D003674:Defense Mechanisms; D005293:Ferritins / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D007501:Iron / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D011494:Protein Kinases / Q000378:metabolism*; D058525:Quartz Crystal Microbalance Techniques; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000378:metabolism*; D046848:White spot syndrome virus 1 / Q000502:physiology*
D014764:Viral Proteins; D005293:Ferritins; D007501:Iron; D011494:Protein Kinases