Fig. 3.

Effect of different Gβγ combinations on EGFR, c-Src, and ERK activity. Rabbit proximal tubule cells were transiently transfected without (mock) or with 10 μg of the expression plasmids for Gβ₁, Gβ₂, Gβ₃, Gβ₄, or Gγ₂. Equal amounts of cell lysates (30 μg) were resolved by SDS-PAGE followed by Western blotting with anti-EGFR, anti-phospho-c-Src (Tyr⁴¹⁶), and anti-phospho-p42MAPK (Try²⁰²)/p44MAPK (Try²⁰⁴) (ERK1/2), and p42MAPK (Try²⁰²)/p44MAPK (Try²⁰⁴) antibodies. Equal protein loading was confirmed by membrane reprobing with anti-EGFR, anti-c-Src, or anti-ERK antibodies. The corresponding bands were scanned, and intensities were normalized to anti-EGFR, anti-c-Src, and anti-ERK from the same tubular cell protein extract. One representative Western blot is shown for every experiment. A: phosphorylation of EGFR (top) compared with total expression of EGFR (bottom). B: phosphorylation of c-Src (p-c-Src; top) compared with total expression of c-Src (bottom). C: phosphorylation of ERK (p-ERK; top) compared with total expression of ERK (bottom). Bar graphs depict the quantitative densitometry analysis for Western blot densitometry data. Values are means ± SE of 4 independent experiments. ***P < 0.001, **P < 0.01 for comparison with control.