Characterization of glutathione proteome in CHO cells and its
relationship with productivity and cholesterol synthesis.
Glutathione (GSH) plays a central role in the redox balance maintenance
in mammalian cells. The study of industrial CHO cell lines have
demonstrated a close link between GSH metabolism and clone productivity.
However, a deep investigation is still required to understand this
correlation and highlights new potential targets for cell engineering.
In this study, we have modulated the GSH intracellular content of an
industrial cell line under bioprocess conditions in order to further
elucidate the role of the GSH synthesis pathway. Two strategies were
used : the variation of cystine supply and the direct inhibition of the
GSH synthesis using buthionine sulfoximine (BSO). Cysteine supply
modulation have revealed a correlation between intracellular GSH and
product titer over time. Analysis of metabolites uptake/secretion rates
and proteome comparison between BSO-treated cells and non-treated cells
has highlighted a slow down of the TCA cycle leading to a secretion of
lactate and alanine in the extracellular environment. Moreover, an
adaptation of the glutathione related proteome has been observed with a
up-regulation of the regulatory subunit of glutamate cysteine ligase and
a down-regulation of a specific glutathione transferase subgroup, the Mu
family. Surprisingly, the main impact of BSO treatment was observed on a
global down-regulation of the cholesterol synthesis pathways. As
cholesterol is required for protein secretion, it can be the missing
part of the jigsaw to finally elucidate the link between GSH synthesis