Reversible lysine acetylation controls the activity of the mitochondrial enzyme acetyl-CoA synthetase 2

Abstract

We report that human acetyl-CoA synthetase 2 (AceCS2) is a mitochondrial matrix protein. AceCS2 is reversibly acetylated at Lys-642 in the active site of the enzyme. The mitochondrial sirtuin SIRT3 interacts with AceCS2 and deacetylates Lys-642 both in vitro and in vivo. Deacetylation of AceCS2 by SIRT3 activates the acetylCoA synthetase activity of AceCS2. This report identifies the first acetylated substrate protein of SIRT3. Our findings show that a mammalian sirtuin directly controls the activity of a metabolic enzyme by means of reversible lysine acetylation. Because the activity of a bacterial ortholog of AceCS2, called ACS, is controlled via deacetylation by a bacterial sirtuin protein, our observation highlights the conservation of a metabolic regulatory pathway from bacteria to humans.eversible lysine acetylation is a highly regulated posttranslational protein modification, which is controlled by protein deacetylases and acetyltransferases (1, 2). Although the importance of reversible lysine acetylation of nuclear nonhistone and histone proteins is well established, the role of protein modification by reversible lysine acetylation in mitochondria is unknown.The nicotinamide (NAM) adenine dinucleotide (NAD ϩ )-dependent deacetylase silent information regulator 2 (sir2) is an important mediator of longevity in response to caloric restriction signals in Saccharomyces cerevisiae, Caenorhabditis elegans, and Drosophila melanogaster (3-9). Seven mammalian Sir2 homologs (SIRT1-7) are known (10-13). The recent discovery that SIRT3, SIRT4, and SIRT5 are found in mitochondria (14-17) suggests the existence of mitochondrial sirtuin substrate proteins. Results and DiscussionAs a strategy to identify lysine-acetylated mitochondrial proteins that could be targeted by SIRT3, -4, or -5, we searched for human proteins with sequence similarity to the region surrounding the acetylated lysine residue found in acetyl-CoA synthetase (ACS) from Salmonella enterica. We chose the acetyl-lysine-containing region of S. enterica ACS, because it is a known substrate for the sirtuin CobB (18,19). In a second step, human proteins showing high similarity were analyzed for their mitochondrial localization probability by using MITOPROT II and PREDOTAR Ver.

NAD+-dependent deacetylation of H4 lysine 16 by class III HDACs

“…Importantly, in mice the only form of SirT3 corresponds to the human processed protein. Both forms of the protein are enzymatically active in the NER assay and both deacetylate H4K16Ac and H3K9Ac in vitro (Scher et al, 2007), whereas the mitochondrial SirT3 protein targets AceCS2, as mentioned above (Schwer et al, 2006). Surprisingly, the global levels of H4K16Ac and H3K9Ac were found to be unaffected in cells knocked down in SirT3 levels by RNAi or in SirT3 À/À MEFs (Scher et al, 2007).…”

“…The best studied is SirT2, the orthologue of yeast Hst2, that is involved in cell-cycle control and regulation of the cytoskeleton (discussed below). SirT3, the closest Sirtuin to SirT2, is found in mitochondria and so far only one mitochondrial target has been identified, AceCS2 (Schwer et al, 2006). However, full-length SirT3 is found in the nucleus, it seems to target histones and is shuttled to the mitochondria under conditions of stress ( Figure 4a); this nuclear function of SirT3 needs to be addressed further (Scher et al, 2007;see below).…”

Sirtuins: critical regulators at the crossroads between cancer and aging

“…SIRT3 functions as a protein deacetylase (Onyango et al, 2002;Schwer et al, 2002), and specifically targets K642 of the mitochondrial protein acetyl-CoA synthetase 2. Deacetylation of acetyl-CoA synthetase 2 activates the enzyme and promotes the production of acetyl-CoA (Hallows et al, 2006;Schwer et al, 2006). Several genetic studies have linked SIRT3 to aging, including in humans (Rose et al, 2003;Glatt et al, 2007).…”

HDAC6, at the crossroads between cytoskeleton and cell signaling by acetylation and ubiquitination

“…Rapid progress in the discovery and functional analysis of an increasing number of nuclear enzymes involved in protein lysine acetylation and deacetylation, histone acetyltransferases (HATs) and histone deacetylases (HDACs), respectively, have demonstrated that these enzymes, independently of transcription, can control some of the basic cellular processes such as protein stability (reviewed in Caron et al, 2005). Moreover, it is now clear that acetylation is not an exclusive modification of nuclear proteins, since many cytoplasmic proteins, including a significant subset of mitochondrial proteins, have recently been shown to bear lysine acetylation (Cohen et al, 2004;Dihazi et al, 2005;Iwabata et al, 2005;Kovacs et al, 2005;Hallows et al, 2006;Kim et al, 2006;Schwer et al, 2006). The regulation of these acetylations and the determination of their functional significance now constitute a real challenge for biologists.…”