Effects of stimulation of AMP-activated protein kinase on insulin-like growth factor 1- and epidermal growth factor-dependent extracellular signal-regulated kinase pathway.
AMP-activated protein kinase (AMPK) is tightly regulated by the cellular AMP:ATP ratio and plays a central role in the regulation of energy homeostasis. Previously, AMPK was reported to phosphorylate serine 621 of Raf-1 in vitro. In the present study, we investigated a possible role of AMPK in extracellular signal-regulated kinase (Erk) cascades, using 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR), a cell-permeable activator of AMPK and antisense RNA experiments. Activation of AMPK by AICAR in NIH-3T3 cells resulted in drastic inhibitions of Ras, Raf-1, and Erk activation induced by insulin-like growth factor 1 (IGF-1). Expression of an antisense RNA for the AMPK catalytic subunit decreased the AMPK activity and significantly diminished the AICAR effect on IGF-1-induced Ras activation and the subsequent Erk activation, indicating that its effect is indeed mediated by AMPK. Phosphorylation of Raf-1 serine 621, however, was not involved in AMPK-mediated inhibition of Erk cascades. In contrast to IGF-1, AICAR did not block epidermal growth factor (EGF)-dependent Raf-1 and Erk activation, but our results demonstrated that multiple Raf-1 upstream pathways induced by EGF were differentially affected by AICAR: inhibition of Ras activation and simultaneous induction of Ras-independent Raf activation. The activities of IGF-1 and EGF receptor were not affected by AICAR. Taken together, our results suggest that AMPK differentially regulate Erk cascades by inhibiting Ras activation or stimulating the Ras-independent pathway in response to the varying energy status of the cell.
Department of Chemistry, Hanyang University, Seoul 133-791, Korea.
J
J
Kim
M Y
MY
Yoon
S L
SL
Choi
I
I
Kang
S S
SS
Kim
Y S
YS
Kim
Y K
YK
Choi
J
J
Ha
D016475:3T3 Cells; D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D019556:COS Cells; D002384:Catalysis; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D004247:DNA / Q000187:drug effects; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D016372:RNA, Antisense / Q000378:metabolism; D012265:Ribonucleotides / Q000494:pharmacology; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection
D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009097:Multienzyme Complexes; D016372:RNA, Antisense; D012265:Ribonucleotides; D005576:Colforsin; D000620:Aminoimidazole Carboxamide; D012694:Serine; D004815:Epidermal Growth Factor; D012313:RNA; D007334:Insulin-Like Growth Factor I; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one