title: Co-expression of foreign proteins tethered to HIV-1 envelope glycoprotein on the cell surface by introducing an intervening second membrane-spanning domain.
abstract: The envelope glycoprotein (Env) of human immunodeficiency virus type I (HIV-1) mediates membrane fusion. To analyze the mechanism of HIV-1 Env-mediated membrane fusion, it is desirable to determine the expression level of Env on the cell surface. However, the quantification of Env by immunological staining is often hampered by the diversity of HIV-1 Env and limited availability of universal antibodies that recognize different Envs with equal efficiency. To overcome this problem, here we linked a tag protein called HaloTag at the C-terminus of HIV-1 Env. To relocate HaloTag to the cell surface, we introduced a second membrane-spanning domain (MSD) between Env and HaloTag. The MSD of transmembrane protease serine 11D, a type II transmembrane protein, successfully relocated HaloTag to the cell surface. The surface level of Env can be estimated indirectly by staining HaloTag with a specific membrane-impermeable fluorescent ligand. This tagging did not compromise the fusogenicity of Env drastically. Furthermore, fusogenicity of Env was preserved even after the labeling with the ligands. We have also found that an additional foreign peptide or protein such as C34 or neutralizing single-chain variable fragment (scFv) can be linked to the C-terminus of the HaloTag protein. Using these constructs, we were able to determine the required length of C34 and critical residues of neutralizing scFv for blocking membrane fusion, respectively.
authors.affiliation: China-Japan Joint Laboratory of Structural Virology and Immunology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Hongyun
authors.initials: H
authors.lastname: Wang
authors.affiliation: China-Japan Joint Laboratory of Structural Virology and Immunology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Li
authors.affiliation: China-Japan Joint Laboratory of Structural Virology and Immunology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; Research Center for Asian Infectious Diseases, Institute of Medical Science, the University of Tokyo, Tokyo, Japan.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Nakane
authors.affiliation: China-Japan Joint Laboratory of Structural Virology and Immunology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Shujun
authors.initials: S
authors.lastname: Liu
authors.affiliation: China-Japan Joint Laboratory of Structural Virology and Immunology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; Research Center for Asian Infectious Diseases, Institute of Medical Science, the University of Tokyo, Tokyo, Japan.
authors.forename: Hirohito
authors.initials: H
authors.lastname: Ishikawa
authors.affiliation: Research Center for Asian Infectious Diseases, Institute of Medical Science, the University of Tokyo, Tokyo, Japan; Division of Infectious Diseases, Advanced Clinical Research Center, Institute of Medical Science, the University of Tokyo, Tokyo, Japan.
authors.forename: Aikichi
authors.initials: A
authors.lastname: Iwamoto
authors.affiliation: China-Japan Joint Laboratory of Structural Virology and Immunology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; Research Center for Asian Infectious Diseases, Institute of Medical Science, the University of Tokyo, Tokyo, Japan.
authors.forename: Zene
authors.initials: Z
authors.lastname: Matsuda
mesh_terms: D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D015700:HIV Envelope Protein gp41 / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008561:Membrane Fusion / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000302:isolation & purification; D017434:Protein Structure, Tertiary / Q000235:genetics; D057127:Single-Chain Antibodies / Q000235:genetics / Q000276:immunology; D053586:Virus Internalization
chemical_list: D015700:HIV Envelope Protein gp41; D008562:Membrane Glycoproteins; D057127:Single-Chain Antibodies