Coexpression of Molecular Chaperone BiP Improves Immunoglobulin Solubility and IgG Secretion from Trichoplusia ni Insect Cells

Abstract

Infection of Trichoplusia ni (BTI-TN5B1-4) insect cells with a baculovirus coding for immunoglobulin G resulted in significant intracellular insolubility of the immunoglobulin chains. In order to increase the immunoglobulin solubility, the chaperone BiP was coexpressed in the insect cells using a separate baculovirus vector. This heterologous BiP was observed to associate with immunoglobulin chains in vivo and enhance the level of soluble intracellular and secreted IgG obtained from T.ni. Pulse chase studies indicated that the heterologous BiP increased the level of soluble nascent immunoglobulin chains and assembly intermediates to suggest that BiP is acting as a true molecular chaperone. The effect of heterologous BiP became more significant with time post-infection as secreted IgG levels increased by 90% after 3.4 days of baculovirus infection. Even following the treatment of cells with tunicamycin, BiP coexpression still enhanced immunoglobulin solubility and secretion to indicate that BiP does not function specifically to retain unglycosylated proteins in the endoplasmic reticulum. Thus, coexpression of a molecular chaperone may be used to enhance cellular productivity and protein secretion provided that the chaperone is involved with post-translational processing and significant protein aggregation is observed.

Improved antibody production in Chinese hamster ovary cells by ATF4 overexpression

“…PDI overexpression increased the secretion of heterologous protein (Mohan et al 2007). BiP overexpression also increased heterologous protein secretion (Hsu and Betenbaugh 1997). In CHO-K1 cells, XBP1s overexpression improved the secretion of several heterologous proteins (Ku et al 2008;Tigges and Fussenegger 2006).…”

Thioredoxin Domain Non-equivalence and Anti-chaperone Activity of Protein Disulfide Isomerase Mutants in Vivo

“…3b). The light chain was also observed although the levels detected were lower since the polyclonal antibody is not as sensitive to light chain (40). There were some differences in the total immunoglobulin and PDI levels detected due to the relative difficulty in obtaining exact viral titer measurements for the equivalent coinfections.…”

Production and characterization of the ectodomain of E2 envelope glycoprotein of hepatitis C virus folded in the presence of full-length E1 glycoprotein

“…Thus, it has been described that co-expression of both protein disulfide isomerase and the chaperone BiP increased the solubility and secretion of immunoglobulin G from insect cell [25,26]. The postulated chaperone-like function of E1 is not translated into higher quantity but its coexpression gives rise to a slightly more compact E2 ectodomain with a lower tendency to form disulfide-bridge oligomers.…”