Activation of IKKβ (a, b, e and f), p65 (c, d, g and h), STAT1 (i–l) and ERK1/2 (m–p) in ARRB1 or ARRB2 knockout BMDMs with or without LPS plus IFN-γ stimulation for 2 h. q–r Interaction of ARRB1 or ARRB2 with p65. BMDMs were stimulated with LPS plus IFN-γ for 1 h and the cell lysates were immunoprecipitated with antibodies against ARRB1 (q) or ARRB2 (r). s Effect of ARRB1 knockout on ARRB2 interaction with p65. t Effect of ARRB2 knockout on ARRB1 interaction with p65. Blots shown in m–p are representatives of three independent experiments. Quantitative data are mean ± s.e. (n = 3). *P < 0.05, **P < 0.01, and ***P < 0.001.