Nitro-fatty acids as activators of hSIRT6 deacetylase activity

Abstract

Sirtuin 6, SIRT6, is critical for both glucose and lipid homeostasis and is involved in maintaining genomic stability under conditions of oxidative DNA damage such as those observed in age-related diseases. There is an intense search for modulators of SIRT6 activity, however, not many specific activators have been reported. Long acyl-chain fatty acids have been shown to increase the weak in vitro deacetylase activity of SIRT6 but this effect is modest at best. Herein we report that electrophilic nitro-fatty acids (nitro-oleic acid and nitro-conjugated linoleic acid) potently activate SIRT6. Binding of the nitro-fatty acid to the hydrophobic crevice of the SIRT6 active site exerted a moderate activation (2-fold at 20 µM), similar to that previously reported for non-nitrated fatty acids. However, covalent Michael adduct formation with Cys18, a residue present at the N-terminus of SIRT6 but absent from other isoforms, induced a conformational change that resulted in a much stronger activation (40-fold at 20 µM). Molecular modeling of the resulting Michael adduct suggested stabilization of the co-substrate and acyl binding loops as a possible additional mechanism of SIRT6 activation by the nitro-fatty acid. Importantly, treatment of cells with nitro-oleic acid promoted H3K9 deacetylation, while oleic acid had no effect. Altogether, our results show that nitrated fatty acids can be considered a valuable tool for specific SIRT6 activation, and that SIRT6 should be considered as a molecular target for in vivo actions of these anti-inflammatory nitro-lipids.

SIRT6 stabilization and cytoplasmic localization in macrophages regulates acute and chronic inflammation in mice

“…Interestingly, the SIRT6 catalytic pocket accommodates long-chain fatty acids, which stimulate the deacetylase activity (14). More recently, we have shown that long chain nitro-fatty acids potentiate SIRT6 deacetylase activity even in the presence of long chain fatty acids (15), suggesting that fatty acids are important players in the regulation of SIRT6. Notably, recent findings show that in cultured macrophages and mouse embryonic fibroblasts (MEFs), SIRT6 efficiently removes fatty acid groups from proteins.…”

Fatty acid nitroalkene reversal of established lung fibrosis

“…Thus, native fatty acids have no impact on cell and tissue inflammatory responses at the nM to low μM concentration ranges where small molecule electrophiles induce signaling responses and no toxicity. Notably, even the 10-nitro derivative of octadecanoic (stearic) acid, a nitroalkane lacking the crucial 9,10 double bond of 10-nitro-octadec-9-enoic acid, displays none of the signaling activities or cell/tissue responses induced by the nitroalkene NO 2 -OA [ 32 , 68 , [72] , [73] , [74] , [75] ]. Preliminary studies in the present PCLS model of fibrosis revealed no native oleic acid effects.…”

Upregulating sirtuin 6 ameliorates glycolysis, EMT and distant metastasis of pancreatic adenocarcinoma with krüppel-like factor 10 deficiency

“…In this study, LA was used at physiological concentrations to induce a conformational change that activated SIRT6 acetylation activity, which was not observed with other sirtuins 12 . A recent study revealed that nitrated fatty acids with a Michael adduct resulted in 20-fold stronger activation of SIRT6 39 . An unexpected finding was that the SIRT6 protein level was elevated by LA treatment in our model.…”