FIG. 1.

ErbB receptor phosphorylation and protein amount. A: ARVM cultured for 10 days were treated for 3h with tyrosine kinase inhibitors (PKI 1µM and CGP 1µM) followed by NRG 10 ng/ml for 10 minutes and immunoprecipitation/western blot was performed as indicated. NRG activated both ErbB2 and ErbB4 receptors; PKI blocked NRG-induced activation of ErbB2 whereas CGP did not. Neither PKI nor CGP inhibited NRG action on the ErbB4 receptor. B: ARVM were treated as in A and western blot was performed as indicated including phospho-specific antibodies for ErbB2 and ErbB4. C: ARVM cultured for 10 days were treated for 48h with DMSO 1µl/ml, PKI 1µM, CGP 1µM and western blot was performed for ErbB1/2/4 and actin as loading control. Neither PKI nor CGP reduced the receptor proteins.