Further characterization of the rabies virus glycoproteins produced by virus-infected and G cDNA-transfected cells using a monoclonal antibody, #1-30-44, which recognizes an acid-sensitive epitope.
Expression of rabies virus glycoprotein (G) by G cDNA-transfected mammalian cells resulted in the production of only a fusion-negative form. Low pH-dependent fusion activity, however, was seen when the expression was done under control of the T7 promoter with the help of recombinant vaccinia virus (RVV-T7) that provided T7 RNA polymerase. Fusion-inactive G proteins were transported to the cell surface as being detected by a conformational epitope-specific monoclonal antibody (mAb; #1-46-12). The fusion-inactive G proteins were recognized by most of our 13 conformation-specific mAbs, except for one mAb, #1-30-44, that recognized the low pH-sensitive conformational epitope. When the G gene expression was done with the help of RVV-T7, although most G proteins remained in the epitope-negative form, a small fraction of G gene products were 1-30-44 epitope-positive, and cell fusion activity could be seen when cells were exposed to low pH conditions. From these results, we conclude that acquisition of low pH-dependent fusion activity is closely related to structural maturation of the G protein to form the low pH-sensitive 1-30-44 epitope. Such maturation seems to be dependent on certain rabies virus-induced cellular conditions or functions, which might also be provided in part by the vaccinia virus infection. We further assume that expression of G cDNA alone mostly results in the production of mis-folded and/or differently folded forms of G protein, and only a small fraction is correctly folded even under RVV-T7-mediated expression conditions.
Kankanamge
Pushpa Jenette
PJ
Department of Molecular Microbiology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
Irie
Takashi
T
Shoji
Jun'ichi
J
Tochikura
Tadafumi S
TS
Kawai
Akihiko
A
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology; D000956:Antigens, Viral / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D019556:COS Cells; D002459:Cell Fusion; D002460:Cell Line; D006224:Cricetinae; D018076:DNA, Complementary / Q000235:genetics; D000939:Epitopes / Q000276:immunology*; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D011233:Precipitin Tests; D011487:Protein Conformation; D017510:Protein Folding; D011820:Rabies virus / Q000276:immunology*; D014162:Transfection; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000956:Antigens, Viral; D018076:DNA, Complementary; D000939:Epitopes; D006023:Glycoproteins; D014759:Viral Envelope Proteins; C064951:glycoprotein G, Rabies virus