title: LKB1 signalling attenuates early events of adipogenesis and responds to adipogenic cues.
abstract: cAMP-response element-binding protein (CREB) is required for the induction of adipogenic transcription factors such as CCAAT/enhancer-binding proteins (C/EBPs). Interestingly, it is known from studies in other tissues that LKB1 and its substrates AMP-activated protein kinase (AMPK) and salt-inducible kinases (SIKs) negatively regulate gene expression by phosphorylating the CREB co-activator CRTC2 and class IIa histone deacetylases (HDACs), which results in their exclusion from the nucleus where they co-activate or inhibit their targets. In this study, we show that AMPK/SIK signalling is acutely attenuated during adipogenic differentiation of 3T3-L1 preadipocytes, which coincides with the dephosphorylation and nuclear translocation of CRTC2 and HDAC4. When subjected to differentiation, 3T3-L1 preadipocytes in which the expression of LKB1 was stably reduced using shRNA (Lkb1-shRNA), as well as Lkb1-knockout mouse embryonic fibroblasts (Lkb1(-/-) MEFs), differentiated more readily into adipocyte-like cells and accumulated more triglycerides compared with scrambled-shRNA-expressing 3T3-L1 cells or Wt MEFs. In addition, the phosphorylation of CRTC2 and HDAC4 was reduced, and the mRNA expression of adipogenic transcription factors Cebpa, peroxisome proliferator-activated receptor γ (Pparg) and adipocyte-specific proteins such as hormone-sensitive lipase (HSL), fatty acid synthase (FAS), aP2, GLUT4 and adiponectin was increased in the absence of LKB1. The mRNA and protein expression of Ddit3/CHOP10, a dominant-negative member of the C/EBP family, was reduced in Lkb1-shRNA-expressing cells, providing a potential mechanism for the up-regulation of Pparg and Cebpa expression. These results support the hypothesis that LKB1 signalling keeps preadipocytes in their non-differentiated form.
authors.affiliation: Department of Experimental Medical ScienceLund University, BMC C11, 221 84 Lund, SwedenDepartment of BiomedicineKarolinska Institute, Stockholm, Sweden.
authors.forename: Amélie
authors.initials: A
authors.lastname: Gormand
authors.affiliation: Department of Experimental Medical ScienceLund University, BMC C11, 221 84 Lund, SwedenDepartment of BiomedicineKarolinska Institute, Stockholm, Sweden.
authors.forename: Christine
authors.initials: C
authors.lastname: Berggreen
authors.affiliation: Department of Experimental Medical ScienceLund University, BMC C11, 221 84 Lund, SwedenDepartment of BiomedicineKarolinska Institute, Stockholm, Sweden.
authors.forename: Lahouari
authors.initials: L
authors.lastname: Amar
authors.affiliation: Department of Experimental Medical ScienceLund University, BMC C11, 221 84 Lund, SwedenDepartment of BiomedicineKarolinska Institute, Stockholm, Sweden.
authors.forename: Emma
authors.initials: E
authors.lastname: Henriksson
authors.affiliation: Department of Experimental Medical ScienceLund University, BMC C11, 221 84 Lund, SwedenDepartment of BiomedicineKarolinska Institute, Stockholm, Sweden.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Lund
authors.affiliation: Department of Experimental Medical ScienceLund University, BMC C11, 221 84 Lund, SwedenDepartment of BiomedicineKarolinska Institute, Stockholm, Sweden.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Albinsson
authors.affiliation: Department of Experimental Medical ScienceLund University, BMC C11, 221 84 Lund, SwedenDepartment of BiomedicineKarolinska Institute, Stockholm, Sweden Olga.Goransson@med.lu.se.
authors.forename: Olga
authors.initials: O
authors.lastname: Göransson
mesh_terms: D041721:3T3-L1 Cells; D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D021581:Active Transport, Cell Nucleus; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism; D050156:Adipogenesis / Q000235:genetics / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D055786:Gene Knockout Techniques; D006655:Histone Deacetylases / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism
chemical_list: C504923:Crtc2 protein, mouse; D034741:RNA, Small Interfering; D014157:Transcription Factors; C474808:salt-inducible kinase-2, mouse; D017346:Protein Serine-Threonine Kinases; C571369:SIK3 protein, mouse; C491654:Stk11 protein, mouse; D055372:AMP-Activated Protein Kinases; C498618:Hdac5 protein, mouse; D006655:Histone Deacetylases
keywords: AMPK; CRTC2; HDACs; LKB1; SIKs; adipogenesis