Levels of EGFR protein correlate with levels and activities of Cα and Cβ in HeLa cells. (a) HeLa cells incubated with RNAi against Cα and Cβ and monitored for PKA-specific phosphotransferase activity in cell extracts of 1 mg/mL. Relative values given as counts per minute (cpm). (b) Relative EGFR mRNA expression levels were measured by RT-PCR and are given as E/G × 100 where E and G are the relative copy numbers of EGFR and GAPDH mRNA, respectively. The results are given as +/- SEM where n = 3. (c) Western immunoblotting analysis of expression of EGFR and PKA C. An anti-actin antibody was applied to ensure equal loading.