Identification of CKIP-1 as a negative regulator in NF-κB activation.

<p>(A) 400 pmol of human CKIP-1-specific siRNA or non-targeting siRNA together with 5 µg of κB-Luc, 0.1 µg of <i>Renilla</i>-Luc were electroporated into Jurkat T cells. Luciferase activity was assayed after 48 hr. The reduction of endogenous CKIP-1 protein levels was analyzed by Western blotting. (B) Jurkat T cells were electroporated with human CKIP-1-specific siRNA or non-targeting siRNA using AMAXA Nucleofector System (Lonza). Thirty hours later, nuclear protein extracts were harvested and NF-κB activity was measured by TransAM NF-κB p65 chemi kit (Active Motif). The reduction of endogenous CKIP-1 protein levels was analyzed by Western blotting. (C) Jurkat T cells were transfected with 5 µg of CKIP-1 or empty vector (mock) together with 5 µg of κB-Luc and 0.1 µg of <i>Renilla</i>-Luc. Nineteen hours later, cells were stimulated for 5 hr upon CD3 (2 µg/ml), CD3/CD28 (2 µg/ml each), TNFα (20 ng/ml), PMA (10 ng/ml) or PMA (10 ng/ml) + CD28 (2 µg/ml). The expressed protein levels were analyzed by Western blotting. (D) Jurkat T cells were transfected with 5 µg of CKIP-1 or empty vector (mock). Twenty-four hours later, cells were stimulated for 30 min upon PMA (10 ng/ml). Then cells were harvested and NF-κB activity was measured by TransAM NF-κB p65 chemi kit. The expressed protein levels were analyzed by Western blotting. Values represent the average of three independent experiments and error bars represent the SD from the average.