The Arabidopsis Class II Sirtuin Is a Lysine Deacetylase and Interacts with Mitochondrial Energy Metabolism      

Abstract

The posttranslational regulation of proteins by lysine (Lys) acetylation has recently emerged to occur not only on histones, but also on organellar proteins in plants and animals. In particular, the catalytic activities of metabolic enzymes have been shown to be regulated by Lys acetylation. The Arabidopsis (Arabidopsis thaliana) genome encodes two predicted sirtuin-type Lys deacetylases, of which only Silent Information Regulator2 homolog (SRT2) contains a predicted presequence for mitochondrial targeting. Here, we have investigated the function of SRT2 in Arabidopsis. We demonstrate that SRT2 functions as a Lys deacetylase in vitro and in vivo. We show that SRT2 resides predominantly at the inner mitochondrial membrane and interacts with a small number of protein complexes mainly involved in energy metabolism and metabolite transport. Several of these protein complexes, such as the ATP synthase and the ATP/ADP carriers, show an increase in Lys acetylation in srt2 loss-of-function mutants. The srt2 plants display no growth phenotype but rather a metabolic phenotype with altered levels in sugars, amino acids, and ADP contents. Furthermore, coupling of respiration to ATP synthesis is decreased in these lines, while the ADP uptake into mitochondria is significantly increased. Our results indicate that SRT2 is important in fine-tuning mitochondrial energy metabolism.Mitochondria are central hubs of energy metabolism in plants and animals. In addition to a fine-tuned mitochondria-to-nuclear signaling that regulates transcription of nuclear gene expression (Rhoads and Subbaiah, 2007;Schwarzländer et al., 2012), posttranslational modifications of proteins are thought to be essential for the regulation of central metabolic pathways and thus determine the plasticity of plant metabolism (Hartl and Finkemeier, 2012). In mammalian mitochondria, the regulation of metabolic functions by posttranslational

The EF-Hand Ca2+ Binding Protein MICU Choreographs Mitochondrial Ca2+ Dynamics in Arabidopsis

“…Mitochondrial protein (800 mg) was isolated and trypsinated, and 1 mg of peptides was analyzed using an EASY-nLC 1000 (Thermo Scientific) coupled to a Q Exactive Plus mass spectrometer (Thermo Scientific) with column and gradient as described (König et al, 2014). Mass spectra were acquired in a data-dependent manner, with an automatic switch between MS and MS/MS scans using a top 12 method.…”

Sirtuins: not only animal proteins

“…These include proteins associated with the inner mitochondrial membrane, i.e., ATP synthase and ATP/ADP carriers. Since the ATP synthesis is a regulator of energy metabolism in mitochondria, changes in the activity of this enzyme can in consequence alter the mitochondrial metabolism (König et al 2014). Van Der Kelen et al (2013) showed that reducing the expression of AtSIR2 decreased the response to salt stress.…”

“…The AtSRT2 gene probably encodes seven isoforms of the RT2 protein. The study of König et al (2014) showed the presence of two isoforms (AtSRT2A and AtSRT2B) that contained pre-sequences on the N-terminal corresponding to the mitochondrial SIR2; they corresponded to SRT2.1/SRT2.2/SRT2.3/SRT2.5 and SRT2.7 isoforms. Studies using C-terminal GFP fusion with AtSRT2 and Western blots showed mitochondrial localization of these isoforms.…”

“…AtSRT1 belongs to class IV and AtSRT2 to class II (Pandey et al 2002;Hollender and Liu 2008). König et al (2014) showed that AtSRT2 has the function of mitochondrial lysine deacetylase. The mitochondrial genome only contains genes encoding the AtSRT2, the presence of genes encoding AtSRT1 have not been detected.…”

“…SIRT1, SIRT2, SIRT3 belong to class I, SIRT4 to class II, SIRT5 to III and SIRT6 and SIRT7 to class IV (Frye 2000;Houtkooper et al 2012). They differ in cell localization, tissue localization, enzymatic activity, substrates and biological implications (Huang et al 2007;Shoba et al 2009;Houtkooper et al 2012;Whitaker et al 2013;König et al 2014;Kupis et al 2016) (Table 1).…”