title: Low glucose-induced ghrelin secretion is mediated by an ATP-sensitive potassium channel.
abstract: Ghrelin is synthesized in X/A-like cells of the gastric mucosa, which plays an important role in the regulation of energy homeostasis. Although ghrelin secretion is known to be induced by neurotransmitters or hormones or by nutrient sensing in the ghrelin-secreting cells themselves, the mechanism of ghrelin secretion is not clearly understood. In the present study, we found that changing the extracellular glucose concentration from elevated (25  mM) to optimal (10 mM) caused an increase in the intracellular Ca2+ concentration ([Ca2+]i) in ghrelin-secreting mouse ghrelinoma 3-1 (MGN3-1) cells (n=32, P<0.01), whereas changing the glucose concentration from elevated to lowered (5 or 1 mM) had little effect on [Ca2+]i increase. Overexpression of a closed form of an ATP-sensitive K+ (KATP) channel mutant suppressed the 10  mM glucose-induced [Ca2+]i increase (n=8, P<0.01) and exocytotic events (n=6, P<0.01). We also found that a low concentration of a KATP channel opener, diazoxide, with 25  mM glucose induced [Ca2+]i increase (n=23, P<0.01) and ghrelin secretion (n≥3, P<0.05). In contrast, the application of a low concentration of a KATP channel blocker, tolbutamide, significantly induced [Ca2+]i increase (n=15, P<0.01) and ghrelin secretion (n≥3, P<0.05) under 5 mM glucose. Furthermore, the application of voltage-dependent Ca2+ channel inhibitors suppressed the 10 mM glucose-induced [Ca2+]i increase (n≥26, P<0.01) and ghrelin secretion (n≥5, P<0.05). These findings suggest that KATP and voltage-dependent Ca2+ channels are involved in glucose-dependent ghrelin secretion in MGN3-1 cells.
authors.affiliation: Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan.
authors.forename: Manami
authors.initials: M
authors.lastname: Oya
authors.affiliation: Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kitaguchi
authors.affiliation: Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Harada
authors.affiliation: Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan.
authors.forename: Rika
authors.initials: R
authors.lastname: Numano
authors.affiliation: Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan.
authors.forename: Masayasu
authors.initials: M
authors.lastname: Kojima
authors.affiliation: Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan takatsuboi@bio.c.u-tokyo.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuboi
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002460:Cell Line; D003981:Diazoxide / Q000494:pharmacology; D005089:Exocytosis; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism; D054439:Ghrelin / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D054086:KATP Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D014044:Tolbutamide / Q000494:pharmacology; D000099161:Kcnj11 Channel
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D003981:Diazoxide; D054439:Ghrelin; D005947:Glucose; D054086:KATP Channels; D050505:Mutant Proteins; D024661:Potassium Channels, Inwardly Rectifying; D014044:Tolbutamide; D000099161:Kcnj11 Channel
keywords: ATP-sensitive potassium channel; calcium channel; exocytosis; ghrelin; glucose; total internal reflection fluorescence microscopy