Figure 4

Association of Tax with activated LKB1 and SIKs. (A) Association with LKB1 in HEK293T cells. Cells were transfected with expression plasmids pCMV-Tag2-LKB1 (WT/D194A) and pCAG-Tax-V5. LKB1 was immunoprecipitated with anti-Flag. The precipitates were analyzed by Western blotting with anti-Flag and anti-Tax, respectively. The input lysates were also immunoblotted for LKB1, Tax and α-tubulin. Detection of phospho-AMPK-T172 (p-AMPK-T172) and total AMPKα2 indicated the kinase activity of LKB1. (B) Association with endogenous LKB1 in T cells. Jurkat, MT2, MT4 and C8166 cells were lysed and immunoprecipitated with anti-Tax. The precipitates were immunoblotted with anti-LKB1 and anti-Tax. A longer exposure (long exp.) of the LKB1 blot is also presented. The input lysates were analyzed for LKB1 and β-actin. (C) Association with SIK1. HEK293T cells were transfected with expression plasmids pCMV-Tag2-SIK1 (WT/K56M) and pCAG-Tax-V5. SIK1 was immunoprecipitated with anti-Flag. The precipitates were analyzed by Western blotting with anti-Flag and anti-Tax. The input lysates were also probed for SIK1, Tax and α-tubulin. (D) Association with SIK2 and SIK3. HEK293T cells were transfected with expression plasmids for pEBG vector (v), pEBG-SIK2 (2), pEBG-SIK3 (3) and pCAG-Tax-V5. GST-SIK2/3 was pulled down by glutathione-Sepharose 4B. The pull-down fraction was analyzed by Western blotting with anti-GST and anti-Tax. The input lysates were also probed for SIK2/3, Tax and α-tubulin.