The epidermal growth factor (EGF) receptor is a 170kD transmembrane tyrosine kinase and member of the HER/ErbB protein family. Ligand binding results in receptor dimerization, autophosphorylation, activation of downstream signaling and lysosomal degradation (1,2). Phosphorylation of EGF receptor (EGFR) at Tyr845 in the kinase domain is implicated in stabilizing the activation loop, maintaining the active state enzyme and providing a binding surface for substrate proteins (3,4). c-Src is involved in phosphorylation of EGFR at Tyr845 (5). The SH2 domain of PLCgamma binds at phospho-Tyr992, resulting in activation of PLCgamma-mediated downstream signaling (6). Phosphorylation of Tyr1045 creates a major docking site for c-Cbl, an adaptor protein that leads to receptor ubiquitination and degradation following EGFR activation (7,8). The GRB2 adaptor protein binds activated EGFR at phospho-Tyr1068 (9). A pair of phosphorylated residues (Tyr1148 and Tyr1173) provide a docking site for the SHC scaffold protein, with both sites involved in MAP kinase signaling activation (2). Phosphorylation of EGFR at specific serine and threonine residues attenuates EGFR kinase activity. EGFR carboxy-terminal residues Ser1046 and Ser1047 are phosphorylated by CaM kinase II, mutations to either of these serines upregulate EGFR tyrosine autokinase activity (10). Sections are cut freshly upon ordering. Description: Each control slide contains formalin fixed, paraffin-embedded MDA-MB-468 cells, both untreated and treated with EGF, that serve as a control for Phospho-EGFR (Tyr1173) immunostaining. Western blot analysis was performed on extracts derived from the same cells to verify the efficacy of the EGF treatment. Applications: These slides are intended for use in immunohistochemical assays. Other applications not tested. Storage: Store at 4C. Optimal staining is achieved if slides are stained following our standard IHC protocols and are used within 8 weeks of assay date, however, signals may persist beyond two months.
