Figure 4.

Cytoplasmic tail of ErbB-1/EGFR inhibits basal phosphorylation of the N1C1 chimera. A) Schematic representation of N1C1 in comparison with the N1C1T1 chimera. Note that the chimeras are identical except for the cytoplasmic tails. B) CHO cells were transfected with plasmids encoding the wild-type ErbB-3, N1C1, or the N1C1T1 chimera. At 48 h after transfection, cells were washed with cold PBS, detached, and lysed. Lysates were cleared, resolved by electrophoresis, and then transferred onto a nitrocellulose membrane. Anti-phosphotyrosine and anti-ErbB-3 antibodies (the latter directed against the extracellular region of the receptor) were used to monitor phosphorylation and verify expression levels, respectively. C) CHO cells were transfected with plasmid encoding the N1C1T1 chimera or they were left untreated. After 48 h, cells were stimulated for 5 min with varying concentrations of NRG, and cell lysates were analyzed as in B.