EGF-induced tyrosine phosphorylation of β2-adaptin is impaired in cells expressing 21KR and various AP-2–binding motif EGFR mutants. PAE cells expressing wtEGFR and various mutants were untreated or treated with 100 ng/ml EGF for 5 min, lysed, and AP-2 was immunoprecipitated (IP) with AP.6 antibody. Immunoprecipitates were blotted with phosphotyrosine antibody (pY20) and antibody to α-adaptin (AC.1). Overexposed blot demonstrates the presence of the weak pY20 signal in AP-2 immunoprecipitates from 21KR-expressing cells. Aliquots of lysates (bottom) were blotted with antibodies to phospho-Tyr1068 of EGFR and total EGFR (1005). Two representative experiments (A and B) are shown.