Activation of AMPK and JNK/MAPK by stresses and ligands.

<p>A: A stable A549 cell line was established by infection of lentivirus carrying LKB1 cDNA. LKB1 expression was examined by Western blot. B: A549 cells and stable A549-LKB1 cells were treated with IL6 (10 ng/ml), TNF-α (10 ng/ml), Adiponectin (10 μg/ml), Anisomycin (10 μg/ml), H₂O₂ (10 mM) and sorbitol (2.5 mM) for 30 min, or AICAR (1mM) for 2 h. Total proteins were extracted and blotted with antibodies as indicated.</p

MLK3 phophorylated AMPKα at T172.

<p>A: HEK293 cells were transfected with empty control, MLK3 or LKB1 vectors. Total proteins were extracted for immunoblotting of pAMPKα-T172 and AMPKα. B: Recombinant AMPK and MLK3 were respectively expressed in HEK293T cells and purified by GSH. <i>In vitro</i> kinase assays were performed as indicated in the presence or absence of AMP. The phosphorylation of AMPK at T172 was determined by western blot analysis.</p

Model of crosstalk between MLK3 and AMPK in stress responses.

<p>Model of crosstalk between MLK3 and AMPK in stress responses.</p

MLK3 physically interacted with AMPKα1.

<p>A: HEK293T cells were transfected with GST-MLK3 or GST-LKB1, and then MLK3 and LKB1 were pulled down with GSH beads and blotted with anti-GST antibody. B: HEK293T cells were transfected with GST empty vector, GST-MLK3 or GST-LKB1, and then recombinant proteins were pulled down with GSH beads and blotted with anti-AMPKα, anti-AMPKα1, as well as anti-AMPKα2. C: GST-MLK3 or GST was co-expressed either with Myc-AMPKα1 or Myc-AMPKα2 in HEK293T cells. Immunoblotting was performed on GSH-pulldown and crude extracts with antibodies against GST and Myc, respectively.</p

The MLK3 signaling pathway.

<p>In response to extracelluar stimuli, MLK3 is dimerized and activated by Cdc42/Rac [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123927#pone.0123927.ref005" target="_blank">5</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0123927#pone.0123927.ref008" target="_blank">8</a>]. Once activated, MLK3 will activate multipe MAP2Ks, which in turn activate the downstream MAPKs by phosphorylation, such as ERK1/2, JNK, or p38 MAPK. The activated MAPKs will further participate in regulating various cellular processes via transcription factors.</p