Dominant negative mutant of AMPK α1 subunit suppresses the effect of AICAR. 3T3-F44a preadipocytes were stably infected with lentivirus expressing a dominant negative mutant of AMPK α1 catalytic subunit (DNα1) tagged with Flag epitope or a control virus (Empty). A. The cells were treated with AICAR and insulin, as described for Figure 1, and assayed for immunoblot with antibodies, as indicated. B. Expression of DNα1 diminishes the endogenous counterpart. The cell extracts containing empty vector (E) or the AMPK mutant (DN) were immunoprecipitated (IP) with anti-flag antibody and equal amounts of pre-IP and post-IP extracts were blotted with anti-flag and anti-AMPK α1 antibodies, respectively. β-actin blot was used as an internal control.