Insect Cells for Heterologous Production of Recombinant Proteins

Abstract

Heterologous gene expression has become an indispensable and powerful tool for the production and subsequent functional analysis of proteins that are difficult to purify from their natural sources. Furthermore, it is the method of choice for the production of variants by introducing site-specific mutations into the DNA encoding the protein of interest. However, many systems are biased by disadvantages. The inability of bacteria to confer important post-translational modifications often results in functional failure of the recombinant protein. In addition, disulfide bonds are not formed properly in bacterial systems. Mammalian cells on the other hand modify properly, but they generally provide low product yields. Insect cells have become an extremely valuable alternative to these established systems. Several cell lines are in use mostly from butterflies and flies. These cells can be infected with insect-specific viruses encoding the desired protein or they are stably transfected with corresponding plasmids for continuous protein production. Besides comparably high product yields, insect cells do glycosylate secreted proteins at appropriate sites, with somewhat altered usage of sugar residues. This often helps to overcome solubility problems and may render the product more homogeneous.