title: Endoplasmic Reticulum-Associated rht-PA Processing in CHO Cells: Influence of Mild Hypothermia and Specific Growth Rates in Batch and Chemostat Cultures.
abstract: BACKGROUND
  Chinese hamster ovary (CHO) cells are the main host for producing recombinant proteins with human therapeutic applications mainly because of their capability to perform proper folding and glycosylation processes. In addition, mild hypothermia is one of the main strategies for maximising the productivity of these systems. However, little information is available on the effect of culture temperature on the folding and degradation processes of recombinant proteins that takes place in the endoplasmic reticulum.
  
  
  METHODS
  In order to evaluate the effect of the mild hypothermia on processing/endoplasmatic reticulum-associated degradation (ERAD) processes, batch cultures of CHO cells producing recombinant human tissue plasminogen activator (rht-PA) were carried out at two temperatures (37°C and 33°C) and treated with specific inhibitors of glycosylation and ERAD I (Ubiquitin/Proteasome system) or ERAD II (Autophagosoma/Lisosomal system) pathways. The effect of mild hypothermia was analysed separately from its indirect effect on specific cell growth rate. To do this, chemostat cultures were carried out at the same incubation conditions as the batch cultures, controlling cell growth at high (0.017 h-1) and low (0.012 h-1) dilution rates. For a better understanding of the investigated phenomenon, cell behaviour was also analysed using principal component analysis (PCA).
  
  
  CONCLUSIONS
  Results suggest that rht-PA is susceptible to degradation by both ERAD pathways studied, revealing that processing and/or ERAD processes are sensitive to temperature cultivation in batch culture. Moreover, by isolating the effect of culture temperature from the effect of cell growth rate verifyed by using chemostat cultures, we have found that processing and/or ERAD processes are more sensitive to reduction in specific growth rate than low temperature, and that temperature reduction may have a positive effect on protein processing. Interestingly, PCA indicated that the integrated performance displayed by CHO cells is modulated predominantly by specific growth rate, indicating that the culture temperature has a lower weighted effect within the range of conditions evaluated in this work.
authors.affiliation: Institute of Chemistry, Pontificia Universidad Católica de Valparaíso, Av. Universidad 330, Curauma, Chile.|School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2085, Valparaíso, 4059, Chile.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Vergara
authors.affiliation: School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2085, Valparaíso, 4059, Chile.
authors.forename: Julio
authors.initials: J
authors.lastname: Berrios
authors.affiliation: School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2085, Valparaíso, 4059, Chile.
authors.forename: Irene
authors.initials: I
authors.lastname: Martínez
authors.affiliation: School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2085, Valparaíso, 4059, Chile.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Díaz-Barrera
authors.affiliation: Biotechnology Center "Dr. Daniel Alkalay Lowitt", Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso, Chile.
authors.forename: Cristian
authors.initials: C
authors.lastname: Acevedo
authors.affiliation: Institute of Chemistry, Pontificia Universidad Católica de Valparaíso, Av. Universidad 330, Curauma, Chile.
authors.forename: Juan G
authors.initials: JG
authors.lastname: Reyes
authors.affiliation: Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States of America.|Department of Bioengineering, Rice University, Houston, Texas, United States of America.
authors.forename: Ramon
authors.initials: R
authors.lastname: Gonzalez
authors.affiliation: School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2085, Valparaíso, 4059, Chile.|CREAS CONICYT Regional GORE Valparaíso R0GI1004. Av. Universidad, Curauma, Chile.
authors.forename: Claudia
authors.initials: C
authors.lastname: Altamirano
mesh_terms: D000818:Animals; D061249:Batch Cell Culture Techniques / Q000379:methods*; D016466:CHO Cells; D049109:Cell Proliferation; D006224:Cricetinae; D003412:Cricetulus; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D060746:Endoplasmic Reticulum-Associated Degradation; D006031:Glycosylation; D006801:Humans; D007036:Hypothermia, Induced; D042541:Intracellular Space / Q000378:metabolism; D025341:Principal Component Analysis; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator