Auto-sumoylation of the Ubc9 E2 SUMO-conjugating Enzyme Extends Cellular Lifespan.

Calorie restriction (CR) provides anti-aging benefits through diverse processes, such as reduced metabolism and growth and increased mitochondrial activity. Although controversy still exists regarding CR-mediated lifespan effects, many researchers are seeking interventions that mimic the effects of CR. Yeast has proven to be a useful model system for aging studies, including CR effects. We report here that yeast adapted through in vitro evolution to the severe cellular stress caused by loss of the Ulp2 SUMO-specific protease exhibit both enhanced growth rates and replicative lifespan, and they have altered gene expression profiles similar to those observed in CR. Notably, in certain evolved ulp2Δ lines, a dramatic increase in the auto-sumoylation of Ubc9 E2 SUMO-conjugating enzyme results in altered regulation of multiple targets involved in energy metabolism and translation at both transcriptional and post-translational levels. This increase is essential for the survival of aged cells and CR-mediated lifespan extension. Thus, we suggest that high Ubc9 auto-sumoylation exerts potent anti-aging effects by promoting efficient energy metabolism-driven improvements in cell replication abilities. This potential could be therapeutically explored for the development of novel CR-mimetic strategies.

Proteomic analysis of host cell protein dynamics in the supernatant of Fc-fusion protein-producing CHO DG44 and DUKX-B11 cell lines in batch and fed-batch cultures.

Chinese hamster ovary (CHO) cells are the most widely used host cell lines for the commercial production of therapeutic proteins including Fc-fusion proteins. During the culture of recombinant CHO (rCHO) cells, host cell proteins (HCPs), secreted from viable cells and released from dead cells, accumulate extracellularly, potentially impairing product quality. In this study, the HCPs that accumulated extracellularly in batch and fed-batch cultures of Fc-fusion protein-producing rCHO cell lines (DG-Fc and DUKX-Fc) were identified and quantified using nanoflow liquid chromatography-tandem mass spectrometry (LC-MS/MS), followed by gene ontology and functional analysis. When the proteome database of Cricetulus griseus was used as a reference to identify the HCPs, more HCPs were identified for DG-Fc (1632 HCPs in batch culture and 1733 HCPs in fed-batch culture) than for DUKX-Fc (1114 HCPs in batch culture and 1002 HCPs in fed-batch culture). Clustering analysis of HCPs, which were classified into four clusters according to their concentration profiles during culture, showed that the concentration profiles of HCPs affecting the quality of Fc-fusion proteins correlated with changes in Fc-fusion protein quality. Taken together, the dataset of HCPs obtained in this study using the two different rCHO cell lines provides insights into the determination of appropriate target proteins to be removed during the culture and purification steps so as to ensure good Fc-fusion protein quality. Biotechnol. Bioeng. 2017;114: 2267-2278. © 2017 Wiley Periodicals, Inc.

Proteomic Analysis of Host Cell Protein Dynamics in the Culture Supernatants of Antibody-Producing CHO Cells.

Chinese hamster ovary (CHO) cells are the most common cell line used for the production of therapeutic proteins including monoclonal antibodies (mAbs). Host cell proteins (HCPs), secreted and released from lysed cells, accumulate extracellularly during the cultures of recombinant CHO (rCHO) cells, potentially impairing product quality. In an effort to maintain good mAb quality during the cultures, HCPs accumulated extracellularly in batch and fed-batch cultures of a mAb-producing rCHO cell line were identified and quantified by nanoflow liquid chromatography-tandem mass spectrometry, followed by their gene ontology and functional analysis. Due to higher cell concentration and longer culture duration, more HCPs were identified and quantitated in fed-batch culture (2145 proteins identified and 1673 proteins quantified) than in batch culture (1934 proteins identified and 1486 proteins quantified). Clustering analysis of HCPs showed that the concentration profiles of HCPs affecting mAb quality (Lgmn, Ctsd, Gbl1, and B4galt1) correlated with changes in mAb quality attributes such as aggregation, charge variants, and N-glycosylation during the cultures. Taken together, the dataset of HCPs obtained in this study provides insights into determining the appropriate target proteins to be removed during both the cultures and purification steps for ensuring good mAb quality.