title: Leptin excites proopiomelanocortin neurons via activation of TRPC channels.
abstract: Leptin can exert its potent appetite-suppressing effects via activation of hypothalamic proopiomelanocortin (POMC) neurons. It depolarizes POMC neurons via activation of a yet unidentified nonselective cation current. Therefore, we sought to identify the conductance activated by leptin using whole-cell recording in EGFP-POMC neurons from transgenic mice. The TRPC channel blockers SKF96365 (1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride), flufenamic acid, and 2-APB (2-aminoethyl diphenylborinate) potently inhibited the leptin-induced current. Also, lanthanum (La(3+)) and intracellular Ca(2+) potentiated the effects of leptin. Moreover, the diacylglycerol-permeable analog OAG (2-acetyl-1-oleoyl-sn-glycerol) failed to activate any TRPC current. Using a Cs(+)-gluconate-based internal solution, the leptin-activated current reversed near -20 mV. After replacement of external Na(+) and K(+) with Cs(+), the reversal shifted to near 0 mV, and the I/V curve exhibited a negative slope conductance at voltages more negative than -40 mV. Based on scRT-PCR, TRPC1 and TRPC4-7 mRNA were expressed in POMC neurons, with TRPC5 being the most prevalent. The leptin-induced current was blocked by the Jak2 inhibitor AG490, the PI3 kinase inhibitor wortmannin, and the phospholipase C inhibitors, U73122 and ET-18-OCH3. Notably, we identified PLCgamma1 transcripts in the majority of POMC neurons. Therefore, leptin through a Jak2-PI3 kinase-PLCgamma pathway activates TRPC channels, and TRPC1, 4, and 5 appear to be the key channels mediating the depolarizing effects of leptin in POMC neurons.
authors.affiliation: Department of Physiology, Oregon National Primate Research Center, Oregon Health & Science University, Portland, Oregon 97239-3089, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Qiu
authors.forename: Yuan
authors.initials: Y
authors.lastname: Fang
authors.forename: Oline K
authors.initials: OK
authors.lastname: Rønnekleiv
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Kelly
mesh_terms: D000818:Animals; D001066:Appetite / Q000187:drug effects / Q000502:physiology; D001896:Boron Compounds / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D005260:Female; D005439:Flufenamic Acid / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics; D007031:Hypothalamus / Q000166:cytology / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D007811:Lanthanum / Q000494:pharmacology; D020738:Leptin / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma / Q000037:antagonists & inhibitors / Q000378:metabolism; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013194:Staining and Labeling; D050052:TRPC Cation Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D001896:Boron Compounds; D002121:Calcium Channel Blockers; D005439:Flufenamic Acid; D049452:Green Fluorescent Proteins; D007093:Imidazoles; D053614:Janus Kinase 2; D007811:Lanthanum; D020738:Leptin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma; D011333:Pro-Opiomelanocortin; D050052:TRPC Cation Channels; C112021:Trpc5 protein, mouse; C485184:enhanced green fluorescent protein; C109986:2-aminoethoxydiphenyl borate; C507926:Jak2 protein, mouse; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole