Increased Heterologous Protein Expression in Drosophila S2 Cells for Massive Production of Immune Ligands/Receptors and Structural Analysis of Human HVEM

Many immune ligands and receptors are potential drug targets, which delicately manipulate a wide range of immune responses. We describe here the successful application of an efficient method to dramatically improve the heterologous expression levels in Drosophila Schneider 2 cells, which enables the high-throughput production of several important immune ligands/receptors for raising antibodies, and for the structural and functional analyses. As an example, we purified the protein and characterized the structure of the immune receptor herpesvirus entry mediator (HVEM, TNFRSF14). HVEM is a member of tumor necrosis factor receptor superfamily, which is recognized by herpes simplex virus glycoprotein D (gD) and facilitates viral entry. HVEM participates in a range of interactions with other cell surface molecules, including LIGHT, BTLA, and CD160 to modulate a wide range of immune processes in CD4⁺ and CD8⁺ T cells, as well as NK cells. Due to the involvement of HVEM in these diverse signaling interactions, crystal structures of HVEM in complex with gD or BTLA have been previously reported. Here, we report the structure of HVEM in the absence of any ligands.