A Krüppel-like factor KLF15 Contributes Fasting-induced Transcriptional Activation of Mitochondrial Acetyl-CoA Synthetase Gene AceCS2

Abstract

Acetyl-CoA synthetase 2 (AceCS2) produces acetylCoA for oxidation through the citric acid cycle in the mitochondrial matrix. AceCS2 is highly expressed in the skeletal muscle and is robustly induced by fasting. Quantification of AceCS2 transcripts both in C2C12 and human myotubes indicated that fasting-induced AceCS2 gene expression appears to be independent on insulin action. Characterization of 5 -flanking region of the mouse AceCS2 gene demonstrates that Krü ppel-like factor 15 (KLF15) plays a key role in the trans-activation of the AceCS2 gene. Deletion and mutation analyses of AceCS2 promoter region revealed that the most proximal KLF site is a curtail site for the trans-activation of the AceCS2 gene by KLF15. Using Sp-null Drosophila SL2 cells, we showed that the combination of KLF15 and Sp1 resulted in a synergistic activation of the AceCS2 promoter. Mutation analyses of three GC-boxes in the AceCS2 promoter indicated that the GC-box, located 8 bases downstream of the most proximal KLF15 site, is the most important GC-box in the synergistic trans-activation of the AceCS2 gene by KLF15 and Sp1. GST pull-down assays showed that KLF15 interacts with Sp1 in vitro. Quantification of various KLF transcripts revealed that 48 h fasting robustly induced the KLF15 transcripts in the skeletal muscle. Together with the trans-activation of the AceCS2 promoter, it is suggested that fasting-induced AceCS2 expression is largely contributed by KLF15. Furthermore, KLF15 overexpression induced the levels of AceCS2 transcripts both in myoblasts and in myotubes, indicating that AceCS2 gene expression in vivo is indeed induced by KLF15.Acetyl-CoA is an important intermediate in various metabolic pathways including fatty acid and cholesterol biosynthesis and the energy production by the citric acid cycle. There are several enzymes that generate acetyl-CoA in the mammals, including pyruvate dehydrogenase, which converts pyruvate to acetyl-CoA without generating free acetate. The degradation of fatty acid via ␤-oxidation system also produces acetyl-CoA as an end product. Although acetate is not an essential source of acetyl-CoA in animals, the enzymatic ligation for the production of acetyl-CoA from acetate and CoA is a key reaction in the catabolism of acetate formed by several conditions including bacterial fermentation in the colon, oxidation of ingested ethanol in the liver. Acetyl-CoA synthetase (AceCS, 1 EC 6.2.1.1) is an enzyme that catalyzes the production of acetyl-CoA from acetate and CoA. In particular, this enzyme plays a key role in the nervous system for recycling of acetate released by acetylcholine esterase for the formation and release of acetylcholine in cholinergic nerve terminals.There are two AceCSs with similar enzymatic properties in mammals: one designated AceCS1 is a cytosolic enzyme and the other, designated AceCS2, is a mitochondrial matrix enzyme (1). Localized in the cytoplasm, AceCS1 provides acetylCoA for the synthesis of fatty acids and cholesterol. In contrast, AceCS2 produces acetyl-CoA for oxida...

Kruppel-like factor 15 is a regulator of cardiomyocyte hypertrophy

“…KLF15 function may involve the regulation of other important transcriptional pathways and physiologic processes in the myocardium. We have previously reported that KLF15 regulates GLUT4 expression in adipose (24) and others have reported that KLF15 regulates mitochondrial acetyl-CoA synthase expression in skeletal muscle (42) and PEPCK expression in hepatocytes (43). In our initial evaluation we did not observe any significant difference in GLUT4 mRNA between KLF15 (ϩ/ϩ) vs. (Ϫ/Ϫ) hearts (data not shown).…”

Kruppel-like Factors (KLFs) in muscle biology

“…Although a number of KLFs have been identified as expressed in developing or mature skeletal muscle (KLF6 [95], KLF13 [47], KLF15 [40]), there are very few reports describing their regulation and potential roles in this tissue (Table 1) [40,96]. Our group has demonstrated that KLF15 is robustly expressed in skeletal muscle where it regulates expression of the glucose transporter GLUT4.…”

“…Recently, we have reported that KLF15(−/−) mice have severe fasting hypoglycemia which is caused by a defect in the ability of critical amino acids to enter the gluconeogenetic pathway in the liver [33] though the significance of this metabolic block in the heart or skeletal muscle has not been fully determined. KLF15 has also been shown to regulate the fasting-induced transcriptional activation of mitochondrial acetyl-CoA sythetase-2 in skeletal muscle [96]. Indeed, a deeper understanding of the expression, regulation and functional significance of KLFs in skeletal muscle has important implications for understanding the molecular pathways perturbed in diseases such as diabetes and metabolic syndrome, congestive heart failure, and peripheral arterial insufficiency [2][3][4].…”

Tissue-specific Short Chain Fatty Acid Metabolism and Slow Metabolic Recovery after Ischemia from Hyperpolarized NMR in Vivo

“…Fast Activation of Acetate to Esters-In vivo NMR spectra of acetate metabolism were recorded in mouse heart, liver, and skeletal muscle supplied with hyperpolarized [1][2][3][4][5][6][7][8][9][10][11][12][13] C]acetate. Hyperpolarized in vivo NMR provides sufficient sensitivity to detect conversion of the marker to different molecular species.…”

“…by a number of enzymes in mammals including pyruvate dehydrogenase, ␤-ketothiolase, and ATP citrate-lyase (1). A less well-explored metabolic pathway forming acetyl-CoA in mammals is the acetyl-CoA synthetase (AceCS)-catalyzed catabolism of acetate ( Fig.…”