IGF-1 phosphorylates AMPK-alpha subunit in ATM-dependent and LKB1-independent manner.
Serine/threonine protein kinase AMP-activated protein kinase (AMPK) is a key metabolic stress-responsive factor that promotes the adaptation of cells to their microenvironment. Elevated concentrations of intracellular AMP, caused by metabolic stress, are known to activate AMPK by phosphorylation of the catalytic subunit. Recently, the tumor suppressor serine/threonine protein kinase LKB1 was identified as an upstream kinases, AMPKKs. In the current study, we found that stimulation with growth factors also caused AMPK-alpha subunit phosphorylation. Interestingly, even an LKB1-nonexpressing cancer cell line, HeLa, exhibited growth factor-stimulated AMPK-alpha subunit phosphorylation, suggesting the presence of an LKB1-independent pathway for AMPK-alpha subunit phosphorylation. In the human pancreatic cancer cell line PANC-1, AMPK-alpha subunit phosphorylation promoted by IGF-1 was suppressed by antisense ataxia telangiectasia mutated (ATM) expression. We found that IGF-1 also induced AMPK-alpha subunit phosphorylation in the human normal fibroblast TIG103 cell line, but failed to do so in a human fibroblast AT2-KY cell line lacking ATM. Immunoprecipitates of ATM collected from IGF-1-stimulated cells also caused the phosphorylation of the AMPK-alpha subunit in vitro. IGF-1-stimulated ATM phosphorylation at both threonine and tyrosine residues, and our results demonstrated that the phosphorylation of tyrosine in the ATM molecule is important for AMPK-alpha subunit phosphorylation during IGF-1 signaling. These results suggest that IGF-1 induces AMPK-alpha subunit phosphorylation via an ATM-dependent and LKB1-independent pathway.
Suzuki
Atsushi
A
Cancer Physiology Project, National Cancer Center Research Institute East, 6-5-1 Kashiwanoha, Kashiwa, Chiba 277-8577, Japan.
Kusakai
Gen-ichi
G
Kishimoto
Atsuhiro
A
Shimojo
Yosuke
Y
Ogura
Tsutomu
T
Lavin
Martin F
MF
Esumi
Hiroyasu
H
D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases; D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D002384:Catalysis; D018797:Cell Cycle Proteins; D002460:Cell Line; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013912:Threonine / Q000737:chemistry; D014162:Transfection; D025521:Tumor Suppressor Proteins; D014443:Tyrosine / Q000737:chemistry
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D025521:Tumor Suppressor Proteins; D013912:Threonine; D014443:Tyrosine; D012313:RNA; D007334:Insulin-Like Growth Factor I; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases