2-Aminopurine inhibits leptin receptor signal transduction
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signal transducer and activator of transcription 3 (STAT3)
extracellular signal-regulated kinase (ERK)
double-strand RNA-activated protein kinase (PKR)
Ob-Rb leptin receptor
Leptin is an important circulating signal for 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 leptin-induced phosporylation 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 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 activation of leptin signal transduction at the level of the Ob-Rb leptin receptor.
European Journal of Pharmacology
Copyright (c) 2006 Elsevier Ltd.