Sirtuin 4 Is a Lipoamidase Regulating Pyruvate Dehydrogenase Complex Activity

Abstract

Summary Sirtuins (SIRTs) are critical enzymes that govern genome regulation, metabolism, and aging. Despite conserved deacetylase domains, mitochondrial SIRT4 and SIRT5 have little to no deacetylase activity, and a robust catalytic activity for SIRT4 has been elusive. Here, we establish SIRT4 as a cellular lipoamidase that regulates the pyruvate dehydrogenase complex (PDH). Importantly, SIRT4 catalytic efficiency for lipoyl- and biotinyl-lysine modifications is superior to its deacetylation activity. PDH, which converts pyruvate to acetyl-CoA, has been known to be primarily regulated by phosphorylation of its E1 component. We determine that SIRT4 enzymatically hydrolyzes the lipoamide cofactors from the E2 component dihydrolipoyllysine acetyltransferase (DLAT), diminishing PDH activity. We demonstrate SIRT4-mediated regulation of DLAT lipoyl levels and PDH activity in cells and in vivo, in mouse liver. Furthermore, metabolic flux switching via glutamine stimulation induces SIRT4 lipoamidase activity to inhibit PDH, highlighting SIRT4 as a guardian of cellular metabolism.

SIRT4 is essential for metabolic control and meiotic structure during mouse oocyte maturation

“…PDKs modulate energy homeostasis in diverse tissues through phosphorylation of the pyruvate dehydrogenase (PDH) complex. In an interesting manner, SIRT4 has been identified as a guardian of cellular metabolism by regulating PDH activity (Mathias et al., 2014). PDH is able to modulate tricarboxylic acid (TCA) cycle in cells, producing ATP and many biosynthetic intermediates in mammalian oocytes.…”

“…We have demonstrated that phosphorylation of Ser293‐PDHE1α results in disruption of meiotic spindle morphology and chromosome movement and lowered total ATP content, probably through inhibition of PDH activity (Hou et al., 2015). It is note that, SIRT4 was recently found to decrease the activity of the PDH complex in human cell lines and mouse models (Mathias et al., 2014). Herein, by employing knockdown and overexpression analysis, we showed that phosphorylation status of Ser293‐PDHE1α is directly or indirectly controlled by SIRT4 expression in mouse oocytes.…”

“…Of them, SIRT4 was shown to be critical for the maintenance of cell metabolism and DNA damage response via modifying glutamate dehydrogenase in mitochondria (Laurent et al., 2012). SIRT4 was also identified as a lipoamidase that inhibits pyruvate dehydrogenase complex (Mathias et al., 2014). However, the function of SIRT4 in mammalian oocytes remains unknown.…”

Metabolic profiling indicates impaired pyruvate dehydrogenase function in myalgic encephalopathy/chronic fatigue syndrome

“…Even if expression of the PPAR target gene ACOX1 was similar in ME/CFS patients and controls, it cannot be excluded that the PPARs contribute in the regulation of PDKs at some stage of ME/CFS disease development (23). The mitochondrial enzyme SIRT4 was recently reported to inhibit PDH activity by hydrolyzing lipoamide cofactors from the E2 component of the PDH complex (21). We found that SIRT4 mRNA expression was upregulated in PBMCs from ME/CFS patients and correlated significantly with mRNA expression of PDK1, PPARA, and PPARD.…”

E4F1 controls a transcriptional program essential for pyruvate dehydrogenase activity

“…The activity of the PDC depends on several cofactors, including lipoate, CoEnzymeA (CoA), FAD+, NAD+, and thiamine pyrophosphate, the latter being imported in the mitochondria by the SLC25A19 transporter (4). So far, finetuning of PDC activity has been mainly attributed to posttranslational modifications of its subunits (5,6), including the extensively studied phosphorylation of PDHA1/E1 modulated by PDH kinases (PDK1-4) and phosphatases (PDP1-2). However, in lower organisms, such as Escherichia coli and Candida albicans, PDC is also controlled at the transcriptional level by the coordinated regulation of genes encoding its components and regulators (7,8).…”