JNK activity is required for E-R3–dependent survival signal. (A) HUVECs transduced with E-R3 chimera untreated or treated with 10 ng/mL EGF pretreated with 1 μM mock peptide (TAT) or JNK inhibitory peptide (JNKI1) as indicated. The synthetic peptide JNKI1 specifically inhibits JNK1/2 activity measured by phosphorylation of the recombinant GST–c-JUN 1-79 in vitro assessed by phosphospecific antibodies. The same extracts were assayed for ERK and AKT phosphorylation with phosphospecific antibodies. (B) Quantification by TUNEL staining of apoptotic HUVECs pretreated with mock peptide (TAT) or with JNK inhibitory peptide (JNKI1). (C-D) Chemotaxis and mitogenic response of HUVECs treated as in panel A in the presence of TAT or JNKI1 as indicated. (E) Western blot analysis of JNK1/2 silencing obtained by transducing HUVECs with lentiviral vectors expressing JNK1 and JNK2 shRNA. (F) Quantification by TUNEL staining of HUVEC apoptosis of cells expressing a mock lentiviral construct or JNK1/2 shRNAas indicated. (G-H) Chemotaxis and mitogenic response of HUVECs either mock infected or silenced by retroviral infection with a vector expressing JNK1/2 shRNA. The results are expressed as the mean ± SD of 3 independent experiments.