title: 2-Aminopurine inhibits leptin receptor signal transduction.
abstract: Leptin is an important circulating signal for the regulation of food intake and body weight. In the present study, we investigated the effect of 2-aminopurine (2-AP), an inhibitor of double-strand RNA-activated protein kinase (PKR), on leptin signal transduction. 2-AP dose-dependently inhibited the leptin-induced phosphorylation of signal transducer and activator of transcription 3 (STAT3), extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) in HEK293 cells stably transfected with the Ob-Rb leptin receptor. On the other hand, we observed only slight inhibition of leptin-induced STAT3 activation by purine treatment, indicating that the inhibitory effect will be dramatically enhanced in the presence of an amino group. 2-AP did not inhibit PMA-induced ERK activation, indicating that the effect may be leptin-signal specific. The inhibitory effect of 2-AP was not mediated by newly synthesized protein because the inhibitory effect of 2-AP on leptin-induced STAT3 activation was not abrogated in the presence of the protein synthesis inhibitor cycloheximide. Interestingly, leptin did not induce PKR activation, suggesting that the effect of 2-AP on the leptin signal may be independent of PKR. Finally, 2-AP inhibited leptin-induced phosphorylation of the Ob-Rb leptin receptor. These results provide evidence of a novel action of 2-AP, i.e., inhibition of the activation of leptin signal transduction at the level of the Ob-Rb leptin receptor.
authors.affiliation: Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Hosoi
authors.forename: Naomi
authors.initials: N
authors.lastname: Matsunami
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nagahama
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Okuma
authors.forename: Koichiro
authors.initials: K
authors.lastname: Ozawa
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Takizawa
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Nomura
mesh_terms: D015075:2-Aminopurine / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D003720:Densitometry; D004229:Dithiothreitol / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors* / Q000235:genetics; D054411:Receptors, Leptin; D015398:Signal Transduction / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
chemical_list: C515448:LEPR protein, human; D011500:Protein Synthesis Inhibitors; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D015075:2-Aminopurine; D003513:Cycloheximide; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate; D004229:Dithiothreitol