title: Human serum activates CIDEB-mediated lipid droplet enlargement in hepatoma cells.
abstract: Human hepatocytes constitutively express the lipid droplet (LD) associated protein cell death-inducing DFFA-like effector B (CIDEB). CIDEB mediates LD fusion, as well as very-low-density lipoprotein (VLDL) maturation. However, there are limited cell culture models readily available to study CIDEB's role in these biological processes, as hepatoma cell lines express negligible levels of CIDEB. Recent work has highlighted the ability of human serum to differentiate hepatoma cells. Herein, we demonstrate that culturing Huh7.5 cells in media supplemented with human serum activates CIDEB expression. This activation occurs through the induced expression of PGC-1α, a positive transcriptional regulator of CIDEB. Coherent anti-Stokes Raman scattering (CARS) microscopy revealed a correlation between CIDEB levels and LD size in human serum treated Huh7.5 cells. Human serum treatment also resulted in a rapid decrease in the levels of adipose differentiation-related protein (ADRP). Furthermore, individual overexpression of CIDEB was sufficient to down-regulate ADRP protein levels. siRNA knockdown of CIDEB revealed that the human serum mediated increase in LD size was CIDEB-dependent. Overall, our work highlights CIDEB's role in LD fusion, and presents a new model system to study the PGC-1α/CIDEB pathway's role in LD dynamics and the VLDL pathway.
authors.affiliation: Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada; National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada.
authors.forename: Ragunath
authors.initials: R
authors.lastname: Singaravelu
authors.forename: Rodney K
authors.initials: RK
authors.lastname: Lyn
authors.forename: Prashanth
authors.initials: P
authors.lastname: Srinivasan
authors.forename: Julie
authors.initials: J
authors.lastname: Delcorde
authors.forename: Rineke H
authors.initials: RH
authors.lastname: Steenbergen
authors.forename: D Lorne
authors.initials: DL
authors.lastname: Tyrrell
authors.forename: John P
authors.initials: JP
authors.lastname: Pezacki
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000502:physiology*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D055785:Gene Knockdown Techniques; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D002479:Inclusion Bodies; D008079:Lipoproteins, VLDL / Q000378:metabolism*; D008954:Models, Biological; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D034741:RNA, Small Interfering / Q000235:genetics; D044967:Serum / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C112511:CIDEB protein, human; D008079:Lipoproteins, VLDL; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D034741:RNA, Small Interfering; D014157:Transcription Factors
keywords: ADRP; CARS; CARS microscopy; CIDE; CIDEB; HNF-4α; LD; Lipid metabolism; PGC-1α; PPAR; PPAR-γ co-activator 1α; TG; VLDL; adipose differentiation-related protein; cell death-inducing DFFA-like effector; coherent anti-Stokes Raman scattering; hepatocyte nuclear factor 4α; lipid droplet; peroxisome proliferator activated receptor; triglyceride; very low density lipoprotein