title: Differential protein expression following low temperature culture of suspension CHO-K1 cells.
abstract: BACKGROUND
  To ensure maximal productivity of recombinant proteins (rP) during production culture it is typical to encourage an initial phase of rapid cell proliferation to achieve high biomass followed by a stationary phase where cellular energies are directed towards production of rP. During many such biphasic cultures, the initial phase of rapid cell growth at 37 degrees C is followed by a growth arrest phase induced through reduction of the culture temperature. Low temperature induced growth arrest is associated with many positive phenotypes including increased productivity, sustained viability and an extended production phase, although the mechanisms regulating these phenotypes during mild hypothermia are poorly understood.
  
  
  RESULTS
  In this study differential protein expression in suspension CHO-K1 cells was investigated following a reduction of the culture temperature from 37 degrees C to 31 degrees C in comparison to standard batch culture maintained at 37 degrees C using 2D-DIGE (Fluorescence 2-D Difference Gel Electrophoresis) and mass spectrometry (MS). There is only limited proteomic analysis of suspension-grown CHO cells describing a direct comparison of temperature shifted versus non-temperature shifted cultures using 2D-DIGE. This investigation has enabled the identification of temperature-dependent as well as temperature-independent proteomic changes. 201 proteins were observed as differentially expressed following temperature shift, of which 118 were up regulated. Of the 53 proteins identified by MALDI-ToF MS, 23 were specifically differentially expressed upon reduction of the culture temperature and were found related to a variety of cellular functions such as regulation of growth (HNRPC), cap-independent translation (EIF4A), apoptosis (importin-alpha), the cytoskeleton (vimentin) and glycoprotein quality control (alpha glucosidase 2).
  
  
  CONCLUSIONS
  These results indicate the extent of the temperature response in CHO-K1 cells and suggest a number of key regulatory proteins and pathways that are involved in modulating the response of cells to mild hypothermia. Regulation of these identified proteins and pathways could be useful for future approaches to engineer CHO cells for improved recombinant protein production.
authors.affiliation: National Institute for Cellular Biotechnology, Dublin City University, Glasnevin, Dublin 9, Ireland. niraj.kumar2@mail.dcu.ie
authors.forename: Niraj
authors.initials: N
authors.lastname: Kumar
authors.forename: Patrick
authors.initials: P
authors.lastname: Gammell
authors.forename: Paula
authors.initials: P
authors.lastname: Meleady
authors.forename: Michael
authors.initials: M
authors.lastname: Henry
authors.forename: Martin
authors.initials: M
authors.lastname: Clynes
mesh_terms: D000818:Animals; D016466:CHO Cells / Q000166:cytology* / Q000502:physiology*; D018929:Cell Culture Techniques / Q000379:methods*; D006224:Cricetinae; D003412:Cricetulus; D015870:Gene Expression / Q000502:physiology*; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000378:metabolism*; D013696:Temperature
chemical_list: D011994:Recombinant Proteins