The ERK pathway is critical for LMP1 mediation of EphA4 downregulation. (A) BJAB cells were infected with pSIN-, LMP1-, ΔCTAR1-, ΔCTAR2-, or ΔCTAR1/2-expressing lentiviruses for 5 days. EphA4, LMP1, and β-actin were detected by western blotting. EphA4 protein-relative folds were normalized to β-actin and standardized with pSIN vector control. (B) LCLs were treated with 20 μM PD98059, SP600125, LY294002, or 2.5 μM Bay11-7082 for 48 hours. EphA4, phosphorylated (p-) and total (t-) proteins of ERK, JNK, Akt, and IkBα were determined by western blotting. β-actin served as an internal control. EphA4 protein-relative folds were normalized to β-actin and standardized with dimethylsulfoxide solvent control. (C) Knockdown of ERK1/2 in LCLs achieved using a lentivirus expressing shERK1 plus shERK2 for 3 days. Infected cells were selected with 2 µg/mL puromycin for 2 days. EphA4, phospho-ERK, total ERK proteins were then determined by western blotting. EphA4 protein-relative folds were normalized to β-actin and standardized with vector control shLuc.