Since the fetal bovine serum contains growth factors such as EGF，I am wondering whether the EGF induced signalings are continuously activated in cells cultured with serum- supplemented medium? For example，EGF activated PLC induced PIP2 hydrolysis. Does this mean that the PIP2 levels in membrane of cells cultured with serum are very low? Since PIP2 hydrolysis generates DAG and IP3, which in turn induces activation of PKC kinases, does this mean that PKC kinases are continuously activated in cells cultured with serum? In most articles, cells treated with EGF should be starved in serum-free medium before, however I did not observe PIP2 hydrolysis and PKC activation in normally cultured cells.
Hello Lee Yx
Fetal bovine serum is widely used as a universal and representative additive for the culture of countless types of primary and immortalized cells. The precise composition of FBS is unknown because this additive comprises various unidentified, naturally occurring small molecules and proteins which would also include EGF in fluctuating proportions. The utilization of FBS at a concentration of 10%, is currently regarded as a gold standard practice in cell culture protocols, but this concentration may not be optimal for inducing signaling pathways like the one you mentioned namely, EGF activated PLC induced PIP2 hydrolysis, continuously in cells cultured in medium that contain serum.
When cells are treated with EGF you need to starve them of serum because this will help to remove the knowns and the unknowns present in culture, reduce analytical interferences, and provide more reproducible experimental conditions. Moreover, it will reduce basal cellular activity and make the population of proliferating cells more homogenous, since they withdraw from the cell cycle to enter the quiescent G0/G1 phase. So, it is necessary to serum starve the cells before any type of treatment as it helps to induce cell cycle synchronization.
Best.
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