SUMOylation Attenuates the Function of PGC-1α

Abstract

Peroxisome proliferator-activated receptor ␥-coactivator-1␣ (PGC-1␣) is a key coordinator of gene programs in metabolism and energy homeostasis in mammals. It is highly responsive to changes in the cellular environment and physiological status of mammals and regulated by post-translational modifications: acetylation, phosphorylation, and methylation. Here, we show that PGC-1␣ is covalently modified by small ubiquitin-like modifier (SUMO) 1 protein, an important regulator of signaling and transcription. Conserved lysine residue 183 located in the activation domain of PGC-1␣ was identified as the major site of SUMO conjugation. Interestingly, the same Lys residue is also a target for acetylation. Therefore, the E185A mutation disrupting the SUMOylation consensus sequence was utilized to show that SUMOylation plays a role in the regulation of PGC-1␣ function. Our results show that SUMOylation does not have an apparent effect on the subcellular localization or the stability of PGC-1␣, but it attenuates the transcriptional activity of the coactivator, probably by enhancing the interaction of PGC-1␣ with corepressor RIP140. Mutation that abolished the SUMOylation augments the activity of PGC-1␣ also in the context of PPAR␥-dependent transcription. Thus, our findings showing that reversible SUMOylation can adjust the activity of PGC-1␣ add a novel layer to the regulation of the coactivator.The transcriptional coactivator peroxisome proliferator-activated receptor ␥ coactivator-1␣ (or PPARGC1␣ or PGC-1␣) 2 was first isolated from brown fat (1). It was found to be important in the regulation of mitochondrial function and metabolism. Although the PGC-1␣ was initially named according to its function as a coactivator for PPAR␥, it is also able to interact via its N-terminal LXXLL motifs and coactivate with several other nuclear receptors, including estrogen receptor ␣, thyroid hormone receptor ␤, and glucocorticoid receptor, as well as other transcription factors, such as FoxO1 (2-7). PGC-1␣ is regulated by several signaling pathways and post-translational modifications (7 12). Interestingly, the latter phosphorylation sites overlap with two Cdc4 phosphodegrons that, when further phosphorylated at Thr 295 by glycogen synthase kinase 3␤, can target the protein for ubiquitylation and proteasomal degradation (13). Notably, PGC-1␣ contains several acetylation sites, specific lysine residues, spanning the entire protein (14). General control of amino acid synthesis 5 (GCN5) acetyltransferase directly acetylates PGC-1␣, thereby inhibiting its coactivator activity (15). The inhibition may be due to trafficking of PGC-1␣ to subnuclear domains where it interacts with transcriptional repressors, such as RIP140. Conversely, deacetylating activity of SIRT1 can keep PGC-1␣ in an active state and bound to chromatin (14,16).In addition to acetylation and methylation, lysine residues can be covalently modified by ubiquitin and ubiquitin-like proteins. Mammals contain three small ubiquitin-like modifier (SUMO) proteins, SUMO-1, -2, and -3,...

SUMOylation of the Farnesoid X Receptor (FXR) Regulates the Expression of FXR Target Genes

“…2, lanes 6 and 7). The requirement to mutate both the lysine and an adjacent acidic amino acid to inactivate some SUMO consensus sites has been reported previously (11,24). Thus, Lys 122 and Lys 275 of FXR serve as the principal attachment sites for Sumo1.…”

Functional crosstalk of PGC-1 coactivators and inflammation in skeletal muscle pathophysiology

“…SUMOylation of PGC-1 does not change its subcellular localization or stability, but presumably facilitates interaction with receptor-interacting protein 140 (RIP140), a known repressor of PGC-1 [71,72]. Finally, O-linked -N-acetylglucosylation and arginine methylation of PGC-1 contribute to sustained transcription activity of this coactivator [73,74].…”

PIASy mediates hypoxia-induced SIRT1 transcriptional repression and epithelial-to-mesenchymal transition in ovarian cancer cells

“…The SIRT1-reporter construct was made by fusing the proximal promoter region of the human SIRT1 gene (2972/+58) with the firefly luciferase cDNA in a pA3Luc vector. Expression constructs for SIRT1, Sp1, PIAS1, PIASx, PIASy, PIAS3, Ubc9 and shRNA plasmids targeting SIRT1 have been described previously (Langley et al, 2002;Rytinki and Palvimo, 2009;Vicart et al, 2006;Zhang et al, 2009;Zhou et al, 2008). Small interfering RNA sequences were listed in supplementary material Table S1.…”