Sar1A overexpression in Chinese hamster ovary cells and its effects on antibody productivity and secretion

Chinese hamster ovary (CHO) cells are the most widely used for therapeutic antibody production. In cell line development, engineering secretion processes such as folding-related protein upregulation is an effective way of constructing cell lines with high recombinant protein productivity. However, there have been few studies on the transport of recombinant proteins between the endoplasmic reticulum (ER) and the Golgi apparatus. In this study, Sar1A, a protein involved in COPII vesicle formation, was focused on to improve antibody productivity by enhancing COPII vesicle-mediated antibody transport from the ER to the Golgi apparatus, and to clarify its effect on the secretion process. The constructed Sar1A-overexpressing CHO cell lines were batch-cultured, in which they showed an increased specific antibody production rate. The intracellular antibody accumulation and the specific localization of the intracellular antibodies were investigated by chase assay using a translation inhibitor and observed by immunofluorescence-based imaging analysis. The results showed that Sar1A overexpression reduced intracellular antibody accumulation, especially in the ER. The effects of the engineered antibody transport on the antibody's glycosylation profile and the unfolded protein response (UPR) pathway were analyzed by liquid chromatography-mass spectrometry and UPR-related gene expression evaluation, respectively. Sar1A overexpression lowered glycan galactosylation and induced a stronger UPR at the end of the batch culture. Sar1A overexpression enhanced the antibody productivity of CHO cells by modifying their secretion process. This approach could also contribute to the production of not only monoclonal antibodies but also other therapeutic proteins that require transport by COPII vesicles.