Abstract
Chinese hamster ovary (CHO) is the most commonly used host cell line for
therapeutic protein production. Their exposure to highly concentrated
feed solution during fed-batch cultivation can cause an unphysiological
osmolality increase (>300 mOsm/kg) affecting cell
physiology, morphology, and proteome. In a companion article
“Hyperosmolality in CHO Culture: Effects on Cellular Behavior and
Morphology” we show that hyperosmolalities of up to 545 mOsm/kg force
cells to ablate proliferation and gradually increase their volume,
almost triplicating it. CHO cells also exhibit a significant
hyperosmolality-dependent mitochondrial activity increase. To get a
deeper insight into molecular mechanisms involved in these processes, we
performed a comparative quantitative label-free proteome study of
hyperosmolality-exposed vs. control CHO cells. Our analysis revealed key
differentially expressed proteins mediating mitochondrial activation,
oxidative stress amelioration, and cell cycle progression. We also
discovered a previously unknown strong regulation of proteins altering
cell membrane rigidity and permeability. Among others, we detected three
members of septins, filamentous proteins forming diffusion barriers in
the cell, to be highly upregulated in response to hyperosmolality. Taken
together, our observations correlate well with the recent CHO-based
fluxome and transcriptome studies and expose new unknown targets
involved in response to hyperosmotic pressure in mammalian cells.