Ta. Hsu et al., EFFECTS OF CO-EXPRESSING CHAPERONE BIP ON FUNCTIONAL ANTIBODY-PRODUCTION IN THE BACULOVIRUS SYSTEM, Protein expression and purification, 5(6), 1994, pp. 595-603
The assembly pathway of the insect cell Spodoptera frugiperda (Sf-9) w
as engineered to include expression of the murine chaperone immunoglob
ulin heavy chain binding protein (BiP) using the baculovirus vector. T
he impact of BiP coexpression on the production and secretion of funct
ional and soluble recombinant immunoglobulin IgG levels was evaluated.
Recombinant BiP was found to associate specifically with immunoglobul
ins in immunoprecipitation studies. Coinfection of insect cells with a
BiP-containing baculovirus and baculoviruses coding for two different
murine IgG proteins increased intracellular functional antibody activ
ity levels substantially above the levels observed in the absence of B
iP. Soluble intracellular immunoglobulin levels were found to increase
as well. However, secreted functional antibody levels did not increas
e significantly. Also, degradation of heavy chain immunoglobulin in in
sect cells was indicated by the accumulation of lower molecular weight
immunoglobulins at 4 days postinfection. Coexpression of light chains
reduced the level of these lower molecular weight immunoglobulins whi
le BiP coexpression led to enhanced levels. These findings suggest tha
t coexpressed BiP can increase intracellular soluble and functional an
tibody yields but that secretion in the baculovirus-insect cell system
must be limited at some post-translational step. (C) 1994 Academic Pr
ess, Inc.