The Function of TER94 of <i>Spodoptera frugiperda</i> 9 Cells When Infected With Invertebrate Iridescent Virus-6

The 118 L protein in the envelope of the Invertebrate iridescent virus 6 (IIV6) is responsible for binding to receptors on the surface of permissive cells. We previously elucidated its function by silencing its gene and neutralizing the protein with antibodies. In this study, we aimed to identify the cellular protein that interacts with 118 L protein during virus infection. Membrane proteins from Spodoptera frugiperda 9 (Sf9) cells were separated by SDS-PAGE and electro-transferred to a nitrocellulose membrane. Using a virus overlay protein binding assay (VOPBA), the 118 L protein purified by His-tag was shown to interact with a cellular protein larger than 100 kDa. Analysis of the cellular protein by LC-MS/MS revealed that the transitional endoplasmic reticulum ATPase (TER94) was the highest-scoring protein. Docking analysis using the HADDOCK2.4 program confirmed the interaction of 118 L with TER94. Furthermore, a pull-down experiment was performed between the TER94 produced by His-tag in the baculovirus expression system, and the 118 L protein produced by GST-tag in the bacterial expression system. The interaction between these two proteins was visualized by western blot analysis using a monoclonal anti-GST antibody. These results indicate that TER94 is a binding protein for 118 L and plays a significant role in the entry of IIV6 into Sf9 cells.