title: RKIP phosphorylation-dependent ERK1 activation stimulates adipogenic lipid accumulation in 3T3-L1 preadipocytes overexpressing LC3.
abstract: 3T3-L1 preadipocytes undergo adipogenesis in response to treatment with dexamethaxone, 1-methyl-3-isobutylxanthine, and insulin (DMI) through activation of several adipogenic transcription factors. Many autophagy-related proteins are also highly activated in the earlier stages of adipogenesis, and the LC3 conjugation system is required for formation of lipid droplets. Here, we investigated the effect of overexpression of green fluorescent protein (GFP)-LC3 fusion protein on adipogenesis. Overexpression of GFP-LC3 in 3T3-L1 preadipocytes using poly-l-lysine-assisted adenoviral GFP-LC3 transduction was sufficient to produce intracellular lipid droplets. Indeed, GFP-LC3 overexpression stimulated expression of some adipogenic transcription factors (e.g., C/EBPα or β, PPARγ, SREBP2). In particular, SREBP2 was highly activated in preadipocytes transfected with adenoviral GFP-LC3. Also, phosphorylation of Raf kinase inhibitory protein (RKIP) at serine 153, consequently stimulating extracellular-signal regulated kinase (ERK)1 activity, was significantly increased during adipogenesis induced by either poly-l-lysine-assisted adenoviral GFP-LC3 transduction or culture in the presence of dexamethasone, 1-methyl-3-isobutylxanthine, and insulin. Furthermore, RKIP knockdown promoted ERK1 and PPARγ activation, and significantly increased the intracellular accumulation of triacylglycerides in DMI-induced adipogenesis. In conclusion, GFP-LC3 overexpression in 3T3-L1 preadipocytes stimulates adipocyte differentiation via direct modulation of RKIP-dependent ERK1 activity.
authors.affiliation: Department of Internal Medicine, Gyeongsang National University School of Medicine, JinJu, 527-27, Republic of Korea; Institute of Health Sciences, Gyeongsang National University School of Medicine, JinJu, 527-27, Republic of Korea.
authors.forename: Jong Ryeal
authors.initials: JR
authors.lastname: Hahm
authors.affiliation: Department of Biochemistry and Convergence Medical Science, Gyeongsang National University School of Medicine, JinJu, 527-27, Republic of Korea; Institute of Health Sciences, Gyeongsang National University School of Medicine, JinJu, 527-27, Republic of Korea.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Ahmed
authors.affiliation: Department of Biochemistry and Convergence Medical Science, Gyeongsang National University School of Medicine, JinJu, 527-27, Republic of Korea; Institute of Health Sciences, Gyeongsang National University School of Medicine, JinJu, 527-27, Republic of Korea. Electronic address: drkim@gnu.ac.kr.
authors.forename: Deok Ryong
authors.initials: DR
authors.lastname: Kim
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D050156:Adipogenesis; D000818:Animals; D004789:Enzyme Activation; D055785:Gene Knockdown Techniques; D050356:Lipid Metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D049488:Phosphatidylethanolamine Binding Protein / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D051782:Sterol Regulatory Element Binding Protein 2 / Q000378:metabolism; D015854:Up-Regulation
chemical_list: C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D049488:Phosphatidylethanolamine Binding Protein; C539308:Raf kinase inhibitory protein, mouse; C497391:Srebf2 protein, mouse; D051782:Sterol Regulatory Element Binding Protein 2; D048052:Mitogen-Activated Protein Kinase 3
keywords: 3T3-L1; Adipogenesis; ERK1; LC3; Lipid droplets; RKIP