title: Inhibition of AMPK through Lyn-Syk-Akt enhances FcεRI signal pathways for allergic response.
abstract: AMPK was shown to negatively regulate FcεRI activation, and FcεR-mediated Fyn activation can counteract the LKB1/AMPK axis in mast cells. However, the relationship between the major Src family kinase Lyn and AMPK remains poorly defined. Here, we investigate the molecular mechanism for AMPK inhibition by FcεRI-Lyn signaling in rat RBL-2H3 cells. We found that FcεRI activation could rapidly inhibit AMPK activation through increased AMPK phosphorylation at the inhibitory Ser485/491 residues without a change at the activating Th172 residue, and this was accompanied by a reduction of ACC phosphorylation. Using specific inhibitors and gene silencing, we found that such AMPK inhibition involved a signaling cascade through Lyn-Syk-Akt. When AMPK was activated by AICAR, A769662 and metformin, FcεRI-mediated Syk, ERK, JNK and p38 activation, and TNFα release were all inhibited. Consistently, AMPK inhibition by compound C increased FcεRI-mediated Lyn activation. Moreover, AMPK activation dominantly impaired IgE-induced recruitment of signal proteins to the FcεRI by blocking the formation of FcεRIβ-Lyn-Syk, FcεRIγ-Lyn-Syk, and AMPK-FcεRIβ complexes. In vitro kinase assay further revealed the ability of AMPKα2 to phosphorylate FcεRIβ in the complex. In vivo, AMPK activation by metformin could readily reduce vascular permeability and ear swelling in a mouse model of passive cutaneous anaphylaxis mediated by IgE. In summary, our findings demonstrate that IgE-mediated FcεRI activation results in AMPK inhibition through activation of Lyn-Syk-Akt pathway, and as such FcεRI receptor can efficiently propagate Lyn-mediated allergic signaling and response. These results provide important insights into the use of AMPK activators for the treatment of allergic diseases.
  
  
  CONCLUSIONS
  AMPK is inhibited by FcεRI via Lyn-Syk-Akt signaling in RBL-2H3 cells. AMPK inhibition supports FcεRI-mediated Lyn signaling and allergic response. Metformin has inhibitory effect on passive cutaneous anaphylaxis.
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Kai-Chun
authors.initials: KC
authors.lastname: Lin
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Duen-Yi
authors.initials: DY
authors.lastname: Huang
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: De-Wei
authors.initials: DW
authors.lastname: Huang
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Shiang-Jong
authors.initials: SJ
authors.lastname: Tzeng
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan. wwllaura1119@ntu.edu.tw.|Graduate Institute of Medical Sciences, Taipei Medical University, Taipei, Taiwan. wwllaura1119@ntu.edu.tw.
authors.forename: Wan-Wan
authors.initials: WW
authors.lastname: Lin
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D004195:Disease Models, Animal; D006801:Humans; D006967:Hypersensitivity / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism*; D007073:Immunoglobulin E / Q000276:immunology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D008687:Metformin / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021122:Protein Subunits / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017455:Receptors, IgE / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D000072377:Syk Kinase / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D021122:Protein Subunits; D017455:Receptors, IgE; D007073:Immunoglobulin E; D008687:Metformin; D000072377:Syk Kinase; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt; D055372:AMP-Activated Protein Kinases
keywords: AMPK; Akt; Anaphylaxis; Basophils; FcεRI; Syk