Enhancing Protein Expression in HEK-293 Cells by Lowering Culture Temperature

Animal cells and cell lines, such as HEK-293 cells, are commonly cultured at 37 degrees C. These cells are often used to express recombinant proteins. Having a higher expression level or a higher protein yield is generally desirable. As we demonstrate in this study, dropping culture temperature to 33 degrees C, but not lower, 24 hours after transient transfection in HEK-293S cells will give rise to similar to 1.5-fold higher expression of green fluorescent protein (GFP) and a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. By following the time course of the GFP-expressing cells growing at 37 degrees C and 33 degrees C from 24 hours after transfection (including 19 hours recovery at 37 degrees C in the normal growth medium), we found that a mild hypothermia (i.e., 33 degrees C) reduces the growth rate of HEK-293S cells, while increasing cellular productivity of recombinant proteins. As a result, green cells remain undivided in a longer period of time. Not surprisingly, the property of a recombinant protein expressed in the cells grown at 33 degrees C is unaffected, as shown by the use of AMPA receptors. We further demonstrate with the use of PC12 cells that this method may be especially useful when a recombinant protein is difficult to express using a chemical-based, transient transfection method.