title: Thyroid hormone receptor sumoylation is required for preadipocyte differentiation and proliferation.
abstract: Thyroid hormone and thyroid hormone receptor (TR) play an essential role in metabolic regulation. However, the role of TR in adipogenesis has not been established. We reported previously that TR sumoylation is essential for TR-mediated gene regulation and that mutation of either of the two sites in TRα or any of the three sites in TRβ reduces TR sumoylation. Here, we transfected TR sumoylation site mutants into human primary preadiocytes and the mouse 3T3L1 preadipocyte cell line to determine the role of TR sumoylation in adipogenesis. Reduced sumoylation of TRα or TRβ resulted in fewer and smaller lipid droplets and reduced proliferation of preadipocytes. TR sumoylation mutations, compared with wild-type TR, results in reduced C/EBP expression and reduced PPARγ2 mRNA and protein levels. TR sumoylation mutants recruited NCoR and disrupted PPARγ-mediated perilipin1 (Plin1) gene expression, associated with impaired lipid droplet formation. Expression of NCoRΔID, a mutant NCoR lacking the TR interaction domain, partially "rescued" the delayed adipogenesis and restored Plin1 gene expression and adipogenesis. TR sumoylation site mutants impaired Wnt/β-catenin signaling pathways and the proliferation of primary human preadipocytes. Expression of the TRβ K146Q sumoylation site mutant down-regulated the essential genes required for canonical Wnt signal-mediated proliferation, including Wnt ligands, Fzds, β-catenin, LEF1, and CCND1. Additionally, the TRβ K146Q mutant enhanced the canonical Wnt signaling inhibitor Dickkopf-related protein 1 (DKK1). Our data demonstrate that TR sumoylation is required for activation of the Wnt canonical signaling pathway during preadipocyte proliferation and enhances the PPARγ signaling that promotes differentiation.
authors.affiliation: From the Molecular Endocrinology Laboratory, Veterans Affairs Greater Los Angeles Healthcare System and Departments of Medicine and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90073, yyl@ucla.edu.
authors.forename: Yan-Yun
authors.initials: YY
authors.lastname: Liu
authors.affiliation: the Genomic Medicine Program, Methodist Hospital Research Institute, Houston, Texas 77030, and.
authors.forename: Stephen
authors.initials: S
authors.lastname: Ayers
authors.affiliation: From the Molecular Endocrinology Laboratory, Veterans Affairs Greater Los Angeles Healthcare System and Departments of Medicine and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90073.
authors.forename: Anna
authors.initials: A
authors.lastname: Milanesi
authors.affiliation: the Institute of Endocrinology, China Medical University, Shenyang 110001, China.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Teng
authors.affiliation: From the Molecular Endocrinology Laboratory, Veterans Affairs Greater Los Angeles Healthcare System and Departments of Medicine and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90073.
authors.forename: Sina
authors.initials: S
authors.lastname: Rabi
authors.affiliation: From the Molecular Endocrinology Laboratory, Veterans Affairs Greater Los Angeles Healthcare System and Departments of Medicine and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90073.
authors.forename: Ysutada
authors.initials: Y
authors.lastname: Akiba
authors.affiliation: From the Molecular Endocrinology Laboratory, Veterans Affairs Greater Los Angeles Healthcare System and Departments of Medicine and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90073, gbrent@ucla.edu.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Brent
mesh_terms: D017667:Adipocytes / Q000166:cytology*; D001483:Base Sequence; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D017931:DNA Primers; D006801:Humans; D009154:Mutation; D047495:PPAR gamma / Q000235:genetics / Q000502:physiology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000378:metabolism*; D058207:Sumoylation
chemical_list: D017931:DNA Primers; D047495:PPAR gamma; D012333:RNA, Messenger; D011988:Receptors, Thyroid Hormone
keywords: 3T3L1; Adipogenesis; Cell Proliferation; Human Primary Preadipocytes; NCoR; Perilipin1; Peroxisome Proliferator-activated Receptor (PPAR); Sumoylation; TR; Wnt Signaling