title: Synergistic interaction between leptin and cholecystokinin in the rat nodose ganglia is mediated by PI3K and STAT3 signaling pathways: implications for leptin as a regulator of short term satiety.
abstract: Research has shown that the synergistic interaction between vagal cholecystokinin-A receptors (CCKARs) and leptin receptors (LRbs) mediates short term satiety. We hypothesize that this synergistic interaction is mediated by cross-talk between signaling cascades used by CCKARs and LRbs, which, in turn, activates closure of K(+) channels, leading to membrane depolarization and neuronal firing. Whole cell patch clamp recordings were performed on isolated rat nodose ganglia neurons. Western immunoblots elucidated the intracellular signaling pathways that modulate leptin/CCK synergism. In addition, STAT3, PI3K, Src, and MAPK genes were silenced by lentiviral infection and transient Lipofectamine transfection of cultured rat nodose ganglia to determine the effect of these molecules on leptin/CCK synergism. Patch clamp studies showed that a combination of leptin and CCK-8 caused a significant increase in membrane input resistance compared with leptin or CCK-8 alone. Silencing the STAT3 gene abolished the synergistic action of leptin/CCK-8 on neuronal firing. Leptin/CCK-8 synergistically stimulated a 7.7-fold increase in phosphorylated STAT3 (pSTAT3), which was inhibited by AG490, C3 transferase, PP2, LY294002, and wortmannin, but not PD98059. Silencing the Src and PI3K genes resulted in a loss of leptin/CCK-stimulated pSTAT3. We conclude that the synergistic interaction between vagal CCKARs and LRbs is mediated by the phosphorylation of STAT3, which, in turn, activates closure of K(+) channels, leading to membrane depolarization and neuronal firing. This involves the interaction between CCK/Src/PI3K cascades and leptin/JAK2/PI3K/STAT3 signaling pathways. Malfunctioning of these signaling molecules may result in eating disorders.
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Heldsinger
authors.forename: Gintautas
authors.initials: G
authors.lastname: Grabauskas
authors.forename: Il
authors.initials: I
authors.lastname: Song
authors.forename: Chung
authors.initials: C
authors.lastname: Owyang
mesh_terms: D000818:Animals; D020868:Gene Silencing; D015640:Ion Channel Gating / Q000187:drug effects; D053614:Janus Kinase 2 / Q000235:genetics / Q000378:metabolism; D020738:Leptin / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009620:Nodose Ganglion / Q000166:cytology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011949:Receptors, Cholecystokinin / Q000235:genetics / Q000378:metabolism; D054411:Receptors, Leptin / Q000235:genetics / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D012528:Satiety Response / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects*; D012844:Sincalide / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D020738:Leptin; D015221:Potassium Channels; D011949:Receptors, Cholecystokinin; D054411:Receptors, Leptin; D050796:STAT3 Transcription Factor; C494088:Stat3 protein, rat; D019869:Phosphatidylinositol 3-Kinases; C507927:Jak2 protein, rat; D053614:Janus Kinase 2; D016392:Proto-Oncogene Proteins pp60(c-src); D020929:Mitogen-Activated Protein Kinase Kinases; D012844:Sincalide