Figure 1
From: A proposed role for glutamine in cancer cell growth through acid resistance
L-glutamine (Gln) may play an essential role in cancer cell growth through enzymatic release of ammonia for acid resistance. (A) HeLa and MCF-7 cells grow in the absence of Gln with continued supply of buffered medium. HeLa and MCF-7 cells were cultured without Gln at pH 6.3 and 7.3. Culture medium was changed every 8 h to maintain relatively constant pH value. Cell density was determined by the CV staining method. (B) HeLa and MCF-7 cells consume more Gln and release more glutamate (Glu) in culture medium of lower pH. Two pH values, 6.5 and 7.0, were used. Gln and Glu concentrations were determined by mass spectrometric analysis. (C) Inhibition of glutaminase activity results in reduction of cell survival and growth under acidic environment. Relative cell growth indicates the normalized change of cell number after cell growth in different medium for 8 h. A relative cell growth value of 0.05 means 5% additional cell growth compared to that at hour 0. The results shown were the average of 10 independent experiments. Medium pH is buffered by 25 mM PIPES. (D) The GLS1 splice variant GAC exhibits a higher activity than KGA, especially at pH 6.0. Shown here is in vitro activity characterization of GAC and KGA at different pH values. The glutaminase activity was measured by the Glu dehydrogenase-based, two-step glutaminase protocol. The proteins used here contain an N-terminal truncation (residues 1-122) for better expression in E. coli. (E) A schematic diagram to illustrate our hypothesis on the essential role of Gln in cancer cell survival.
