Thyroid hormone receptor sumoylation is required for preadipocyte differentiation and proliferation.

Authors:
Liu YY, Ayers S, Milanesi A, Teng X, Rabi S, Akiba Y, Brent GA
In:
Source: J Biol Chem
Publication Date: (2015)
Issue: 290(12): 7402-15
Research Area:
Basic Research
Cells used in publication:
Adipocyte (pre), human
Species: human
Tissue Origin: adipose
3T3-L1 ad
Species: mouse
Tissue Origin: embryo
Platform:
Nucleofector™ I/II/2b
Experiment
The author hypothesizes that thyroid hormone receptor (TR) and specifically the post-translational modification of this receptor through sumoylation contribute to both preadipocyte proliferation and adipogeneesis. To demonstrate this, the author Nucleofects mutants into sites known to contribute to TR sumoylation of both normal, human preadipocytes (obtained from Lonza) and the 3T3L1 preadipocyte cell line and observes the effects on both proliferation and adipogenesis. The author’s collected data seems demonstrate that TR sumoylation is required for activation of the Wnt canonical signaling pathway during preadipocyte proliferation and enhances PPAR-gamma signaling that promotes differentiation.
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 TRa or any of the three sites in TRß 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 TRa or TRß 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 PPAR?2 mRNA and protein levels. TR sumoylation mutants recruited NCoR and disrupted PPAR?-mediated perilipin1 (Plin1) gene expression, associated with impaired lipid droplet formation. Expression of NCoR?ID, 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/ß-catenin signaling pathways and the proliferation of primary human preadipocytes. Expression of the TRß K146Q sumoylation site mutant down-regulated the essential genes required for canonical Wnt signal-mediated proliferation, including Wnt ligands, Fzds, ß-catenin, LEF1, and CCND1. Additionally, the TRß 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 PPAR? signaling that promotes differentiation.