Cell engineering to optimise protein secretion: Analysis of components of the secretory system

A series of recombinant clones, derived from the mouse NS/0 cell line, have been studied. These three clones secrete varying high levels of h1B4, a humanised monoclonal antibody. The secretion levels of protein have been measured by ELISA and the specific secretion rates calculated. These clones, and a series of wild-type cells have been analysed by western blotting using antibodies against various chaperone proteins and components of the protein secretory system. The activity of protein disulphide isomerase (PDI), the enzyme which catalyses protein folding, has been measured. The three cell lines showed no significant differences in PDI activity or levels of PDI, BiP, and ribophorin II. Further studies of the clones will be aimed at identifying possible rate-or yield-limiting steps in protein secretion.