Baculovirus Utilizes Cholesterol Transporter NIEMANN-Pick C1 for Host Cell Entry.

Zhihong Li,Guoqing Pan,Qiang He,Mengxian Long,Yonghua Zhang,Jie Chen,Youpeng Fan,Xionge Mei,Junhong Wei,Jialing Bao,Zeyang Zhou,Chunfeng Li,Tian Li

doi:10.3389/fmicb.2019.02825

Abstract

The dual roles of baculovirus for the control of natural insect populations as an insecticide, and as a tool for foreign gene expression and delivery, have called for a comprehensive understanding of the molecular mechanisms governing viral infection. Here, we demonstrate that the Bombyx mori Niemann-Pick C1 (BmNPC1) is essential for baculovirus infection in insect cells. Both pretreatment of B. mori embryonic cells (BmE) with NPC1 antagonists (imipramine or U18666A) and down-regulation of NPC1 expression resulted in a significant reduction in baculovirus BmNPV (B. mori nuclear polyhedrosis virus) infectivity. Disruption of BmNPC1 could decrease viral entry (2 hpi) rather than reduce the viral binding to the BmE cells. Furthermore, our results showed that NPC1 domain C binds directly and specifically to the viral glycoprotein GP64, which is responsible for both receptor binding and fusion. Antibody blocking assay also revealed that the domain C specific polyclonal antibody inhibited BmNPV infection, indicating that NPC1 domain C most likely plays a role during viral fusion in endosomal compartments. Our results, combined with previous studies identifying an essential role of human NPC1 (hNPC1) in filovirus infection, suggest that the glycoprotein of several enveloped viruses possess a shared strategy of exploiting host NPC1 proteins during virus intracellular entry events.

Highlights

Enveloped viruses include a number of pathogens with significant importance to animal or human health
To further study the biological function of Bombyx mori Niemann-Pick C1 (BmNPC1) and its role in baculovirus infection in insect cells, the full length (4 kb) coding sequence (CDS) of BmNPC1 was cloned from the B. mori cDNA library (Figure 1B); the sequence was 100% identical to the sequence of XP_012544312.1 published in the NCBI database
Combined with previous studies that human NiemannPick C1 (NPC1) (hNPC1) located on the late endosomes and lysosomes, suggest BmNPC1 located on the late endosomes and lysosomes

Summary

Introduction

Enveloped viruses include a number of pathogens with significant importance to animal or human health. As a typical double-stranded DNA enveloped virus, baculoviruses are known to infect invertebrates, with over 600 host species described (Blissard and Rohrmann, 1990; Wood and Granados, 1991). BV first attaches to the host cell surface, and is internalized by endocytosis to late endosomes (Volkman and Goldsmith, 1985); subsequently, the viral membrane of BV fuses with the endosomal membrane upon low pH trigger, and nucleocapsids are released into cytoplasm followed by viral replication (Kielian and Rey, 2006; Kadlec et al, 2008). The major BV (Group I alphabaculoviruses) envelope protein, glycoprotein 64 (GP64), has been shown to be essential for both virus attachment and membrane fusion (Rahman and Gopinathan, 2003). A number of host molecules including heparin sulfate (Duisit et al, 1999), phospholipids (Tani et al, 2001) or Bombyx mori receptor expression-enhancing protein (BmREEPa) (Dong et al, 2015) have been identified to be involved in BV attachment or binding, the exact identity of host receptors for baculovirus still remains elusive

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Conclusion