title: Salt-inducible Kinase 3 Signaling Is Important for the Gluconeogenic Programs in Mouse Hepatocytes.
abstract: Salt-inducible kinases (SIKs), members of the 5'-AMP-activated protein kinase (AMPK) family, are proposed to be important suppressors of gluconeogenic programs in the liver via the phosphorylation-dependent inactivation of the CREB-specific coactivator CRTC2. Although a dramatic phenotype for glucose metabolism has been found in SIK3-KO mice, additional complex phenotypes, dysregulation of bile acids, cholesterol, and fat homeostasis can render it difficult to discuss the hepatic functions of SIK3. The aim of this study was to examine the cell autonomous actions of SIK3 in hepatocytes. To eliminate systemic effects, we prepared primary hepatocytes and screened the small compounds suppressing SIK3 signaling cascades. SIK3-KO primary hepatocytes produced glucose more quickly after treatment with the cAMP agonist forskolin than the WT hepatocytes, which was accompanied by enhanced gluconeogenic gene expression and CRTC2 dephosphorylation. Reporter-based screening identified pterosin B as a SIK3 signaling-specific inhibitor. Pterosin B suppressed SIK3 downstream cascades by up-regulating the phosphorylation levels in the SIK3 C-terminal regulatory domain. When pterosin B promoted glucose production by up-regulating gluconeogenic gene expression in mouse hepatoma AML-12 cells, it decreased the glycogen content and stimulated an association between the glycogen phosphorylase kinase gamma subunit (PHKG2) and SIK3. PHKG2 phosphorylated the peptides with sequences of the C-terminal domain of SIK3. Here we found that the levels of active AMPK were higher both in the SIK3-KO hepatocytes and in pterosin B-treated AML-12 cells than in their controls. These results suggest that SIK3, rather than SIK1, SIK2, or AMPKs, acts as the predominant suppressor in gluconeogenic gene expression in the hepatocytes.
authors.affiliation: Laboratory of Cell Signaling and Metabolic Disease, National Institute of Biomedical Innovation, Osaka, 567-0085, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Itoh
authors.affiliation: Laboratory of Cell Signaling and Metabolic Disease, National Institute of Biomedical Innovation, Osaka, 567-0085, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Sanosaka
authors.affiliation: Research Center for Medicinal Plant Resources, Tsukuba Division, Ibaraki, 305-0843, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Fuchino
authors.affiliation: Department of Cell Growth and Differentiation, Center for iPS Cell Research and Application, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Yahara
authors.affiliation: Laboratory of Cell Signaling and Metabolic Disease, National Institute of Biomedical Innovation, Osaka, 567-0085, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Kumagai
authors.affiliation: Laboratory of Cell Signaling and Metabolic Disease, National Institute of Biomedical Innovation, Osaka, 567-0085, Japan; Department of Life Science and Biotechnology, Kansai University, Osaka 564-8680, Japan.
authors.forename: Daisaku
authors.initials: D
authors.lastname: Takemoto
authors.affiliation: Laboratory of Cell Signaling and Metabolic Disease, National Institute of Biomedical Innovation, Osaka, 567-0085, Japan.
authors.forename: Mai
authors.initials: M
authors.lastname: Kagawa
authors.affiliation: Department of Food and Nutrition, Senri Kinran University, Osaka, 565-0873 Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Doi
authors.affiliation: Department of Nutrition and Health, Faculty of Human Development, Soai University, Osaka, 559-0033, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Ohta
authors.affiliation: Department of Cell Growth and Differentiation, Center for iPS Cell Research and Application, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Tsumaki
authors.affiliation: Research Center for Medicinal Plant Resources, Tsukuba Division, Ibaraki, 305-0843, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kawahara
authors.affiliation: Laboratory of Cell Signaling and Metabolic Disease, National Institute of Biomedical Innovation, Osaka, 567-0085, Japan. Electronic address: takemori@nibiohn.go.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takemori
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005260:Female; D055786:Gene Knockout Techniques; D005943:Gluconeogenesis / Q000187:drug effects; D005947:Glucose / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D007189:Indans / Q000494:pharmacology; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism
chemical_list: C504923:Crtc2 protein, mouse; D007189:Indans; D014157:Transcription Factors; C586064:pterosin B; D017346:Protein Serine-Threonine Kinases; C571369:SIK3 protein, mouse; D005947:Glucose
keywords: AMP-activated kinase (AMPK); CRTC; SIK; cAMP response element-binding protein (CREB); gluconeogenesis; hepatocyte; liver kinase B1 (LKB1)