title: The Crystal Structure of the Fifth Scavenger Receptor Cysteine-Rich Domain of Porcine CD163 Reveals an Important Residue Involved in Porcine Reproductive and Respiratory Syndrome Virus Infection.
abstract: Porcine reproductive and respiratory syndrome (PRRS) has become an economically critical factor in swine industry since its worldwide spread in the 1990s. Infection by its causative agent, PRRS virus (PRRSV), was proven to be mediated by an indispensable receptor, porcine CD163 (pCD163), and the fifth scavenger receptor cysteine-rich domain (SRCR5) is essential for virus infection. However, the structural details and specific residues of pCD163 SRCR5 involved in infection have not been defined yet. In this study, we prepared recombinant pCD163 SRCR5 in Drosophila melanogaster Schneider 2 (S2) cells and determined its crystal structure at a high resolution of 2.0 Å. This structure includes a markedly long loop region and shows a special electrostatic potential, and these are significantly different from those of other members of the scavenger receptor cysteine-rich superfamily (SRCR-SF). Subsequently, we carried out structure-based mutational studies to identify that the arginine residue at position 561 (Arg561) in the long loop region is important for PRRSV infection. Further, we showed Arg561 probably takes effect on the binding of pCD163 to PRRSV during virus invasion. Altogether the current work provides the first view of the CD163 SRCR domain, expands our knowledge of the invasion mechanism of PRRSV, and supports a molecular basis for prevention and control of the virus.
  
  
  OBJECTIVE
  PRRS has caused huge economic losses to pig farming. The syndrome is caused by PRRSV, and PRRSV infection has been shown to be mediated by host cell surface receptors. One of them, pCD163, is especially indispensable, and its SRCR5 domain has been further demonstrated to play a significant role in virus infection. However, its structural details and the residues involved in infection are unknown. In this study, we determined the crystal structure of pCD163 SRCR5 and then carried out site-directed mutational studies based on the crystal structure to elucidate which residue is important. Our work not only provides structural information on the CD163 SRCR domain for the first time but also indicates the molecular mechanism of PRRSV infection and lays a foundation for future applications in prevention and control of PRRS.
authors.affiliation: College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, Henan, China.|Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China.
authors.forename: Hongfang
authors.initials: H
authors.lastname: Ma
authors.affiliation: College of Chemistry, Fuzhou University, Fuzhou, Fujian, China.
authors.forename: Longguang
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China.
authors.forename: Songlin
authors.initials: S
authors.lastname: Qiao
authors.affiliation: Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China.
authors.forename: Yubao
authors.initials: Y
authors.lastname: Zhi
authors.affiliation: Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China.
authors.forename: Xin-Xin
authors.initials: XX
authors.lastname: Chen
authors.affiliation: Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, Henan, China.|Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Huang
authors.affiliation: College of Chemistry, Fuzhou University, Fuzhou, Fujian, China.
authors.forename: Mingdong
authors.initials: M
authors.lastname: Huang
authors.affiliation: Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China lirui860620@sina.com zhanggaiping2003@163.com.
authors.forename: Rui
authors.initials: R
authors.lastname: Li
authors.affiliation: College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, Henan, China lirui860620@sina.com zhanggaiping2003@163.com.|Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China.
authors.forename: Gai-Ping
authors.initials: GP
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015214:Antigens, Differentiation, Myelomonocytic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D008958:Models, Molecular; D009154:Mutation; D019318:Porcine Reproductive and Respiratory Syndrome / Q000378:metabolism* / Q000821:virology; D019316:Porcine respiratory and reproductive syndrome virus / Q000502:physiology; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D055672:Static Electricity; D013329:Structure-Activity Relationship; D013552:Swine; D000098902:CD163 Antigen
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000098902:CD163 Antigen; D011956:Receptors, Cell Surface
keywords: CD163; Drosophila S2 cells; PRRSV; SRCR5; crystal structure