Protein Phosphorylation Profiling Using an In Situ Proximity Ligation Assay: Phosphorylation of AURKA-Elicited EGFR-Thr654 and EGFR-Ser1046 in Lung Cancer Cells
Figure 3
The EGFR phosphorylation sites showed distinct phosphorylation patterns after EGF stimulation in EGFR-WT and EGFR-mutant cells.
H1299 cells stably expressed the empty vector, EGFR-WT or mutant EGFR-L858R. (A) After stimulation with EGF (10 ng/ml) in serum-free medium for 10 minutes, cell extracts were subjected to immunoblotting analysis with the indicated phospho-tyrosine antibodies. EGF-dependent (EGFR-Tyr992, -Tyr1148 and -Tyr1068) and EGF-independent [EGFR-Tyr845, -Tyr974, -Tyr1086 and -Tyr1101, -Thr654 (see below) and -Ser1046 (see below)] phosphorylation were observed in H1299 cells expressing EGFR-L858R mutant. The phosphorylation of EGFR-Thr654 (B) and -Ser1046 (C) with or without EGF treatment in different lung cancer cell lines was monitored via in situ PLA. The quantification of in situ PLA is shown on the right. EGFR-Thr654 and -Ser1046 were phosphorylated upon EGF treatment in H1299-EGFR-WT cells, whereas their phosphorylation was EGF-independent in H1299-EGFR-L858R cells. (D) Immunoblotting analysis of EGFR-Thr654 and -Ser1046 was performed in EGFR mutant cells (H1975, which contains the EGFR-L858R and -T790M mutants) and cells expressing EGFR-WT (A549). The phosphorylation of EGFR-Tyr1068 was induced by EGF. The phosphorylation of EGFR-Thr654 and -Ser1046 was EGF-independent in H1975 and H1299-EGFR-L858R cells as determined by immunoblotting.