title: Leptin but not ciliary neurotrophic factor (CNTF) induces phosphotyrosine phosphatase-1B expression in human neuronal cells (SH-SY5Y): putative explanation of CNTF efficacy in leptin-resistant state.
abstract: Growing evidences suggest that obesity is associated with hypothalamic leptin resistance, leading to the alteration of food intake control. Alternative treatment using ciliary neurotrophic factor (CNTF) has been suggested because CNTF exerts a leptin-like effect, even in leptin-resistant states, but the mechanisms by which CNTF maintains this effect are not yet understood. Both leptin and CNTF act in the hypothalamus through similar signaling pathways including janus kinase-2/signal transducer and activator of transcription (STAT)-3 pathway. To explore the differences and interactions between leptin and CNTF signaling pathways, differentiated human neuroblastoma cells (SH-SY5Y) were exposed to either leptin or CNTF and then challenged for each cytokine. Leptin pretreatment completely abolished leptin-dependent STAT-3 and ERK 1/2 phosphorylations without affecting CNTF action. The lack of cross-desensitization between leptin and CNTF signaling pathways occurred despite the induction of suppressor of cytokine signaling-3 in response to both cytokines. Interestingly, leptin as well as insulin induced the expression of phosphotyrosine phosphatase (PTP)-1B, whereas CNTF treatment did not affect its expression. In addition, acute leptin treatment but not CNTF induced PTP-1B expression in mouse hypothalamic arcuate nucleus. Furthermore, the overexpression of human PTP-1B in SH-SY5Y cells completely abolished leptin- and insulin-dependent janus kinase-2, STAT-3, and ERK 1/2 phosphorylations, but CNTF action was not altered. Collectively, our results suggest that PTP-1B constitutes a key divergent element between leptin/insulin and CNTF signaling pathways at the neuronal level, which may constitute a possible mechanism that explains the efficacy of CNTF in leptin-resistant states.
authors.affiliation: Neuroendocrinologie Moléculaire de la Prise Alimentaire, Unité Mixte de Recherche 1197, Université Paris-Sud 11, Institut National de la Recherche Agronomique, Orsay, France.
authors.forename: Yacir
authors.initials: Y
authors.lastname: Benomar
authors.forename: Flavien
authors.initials: F
authors.lastname: Berthou
authors.forename: Claire-Marie
authors.initials: CM
authors.lastname: Vacher
authors.forename: Virginie
authors.initials: V
authors.lastname: Bailleux
authors.forename: Arieh
authors.initials: A
authors.lastname: Gertler
authors.forename: Jean
authors.initials: J
authors.lastname: Djiane
authors.forename: Mohammed
authors.initials: M
authors.lastname: Taouis
mesh_terms: D000818:Animals; D002460:Cell Line; D020934:Ciliary Neurotrophic Factor / Q000494:pharmacology*; D004351:Drug Resistance / Q000187:drug effects / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000378:metabolism; D020738:Leptin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000235:genetics* / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D016896:Treatment Outcome; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D020934:Ciliary Neurotrophic Factor; D007328:Insulin; D020738:Leptin; D050796:STAT3 Transcription Factor; C516607:PTPN1 protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1