Baculovirus Utilizes Cholesterol Transporter NIEMANN–Pick C1 for Host Cell Entry

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.

Advances in the Arms Race Between Silkworm and Baculovirus

“…The cholesterol transporter BmNPC1 interacts with GP64. Its deficiency inhibits viral penetration rather than viral binding to BmE cells ( 29 ). In contrast, BmNPV BV uses clathrin- and dynamin-dependent endocytosis pathways to penetrate BmN cells.…”

Identification and Characterization of Genes Related to Resistance of Autographa californica Nucleopolyhedrovirus Infection in Bombyx mori

“…We performed RNAi to the chloride intracellular channel gene and found that the copy numbers of the virus were not significantly changed. As previous report that the NPC-1 gene was an essential host factor in BmNPV infection [ 17 ], therefore the NPC-1 was selected as a candidate gene for further research.…”

“…Previous research has shown that it was also severe as a virus intracellular receptor for filovirus entry, such as Ebola virus and Marburg virus; the mutation of domain C would result in complete resistance to virus infection [ 13 , 14 , 15 , 16 ]. A recent study showed that NPC-1 was also an essential host factor for baculovirus infection in insect cells, it may interact with the GP64 of BmNPV to facilitate the virus’ entry [ 17 ].…”

Two Cholesterol Recognition Amino Acid Consensus Motifs of GP64 with Uncleaved Signal Peptide Are Required for Bombyx mori Nucleopolyhedrovirus Infection

“…Coincidentally, the same phenotype was observed in the viruses with BmNPV GP64 fusion loops that had been mutated in our previous study (Bifang Hao, Lin Liu, Na Liu, Wenbin Nan, Fengxiu Fan, Jinshan Huang, unpublished data). We found that macropinocytosis was employed by BmNPV to invade host cells ( 1 , 22 ), and virions were transported into endolysosomes, in which GP64 interacted with the Niemann-Pick type C1 (NPC1) transporter ( 5 ). NPC1 is a cholesterol transporter that interacts with Ebola virus glycoprotein priming by cathepsin L in the endolysosome and mediates virus infection with other host factors ( 23 ); thus, cholesterol, NPC1, GP64, or other viral proteins may cooperate to mediate BmNPV entry.…”