Identification of Acyl-CoA Thioesterase in Mouse Mesenteric Lymph Nodes

Abstract

Acyl-CoA thioesterases (ACOTs) are a group of enzymes that catalyze the hydrolysis of fatty acyl-CoAs to free fatty acids and CoA, with the potential to regulate the intracellular levels of these molecules. In this study, we show that a cytosolic isoform, ACOT7, is expressed at a significant level in the mesenteric lymph nodes (MLNs) of mice. While crude preparations of the mesenteric visceral fat contained significant levels of palmitoyl-CoA thioesterase activity, enzyme activity was concentrated 6.9-fold in MLNs compared with the residual adipose portion after excision of MLNs. When MLN homogenates were centrifuged, 82% of the enzyme activity was recovered in the cytosolic fraction, concomitant with almost exclusive recovery of ACOT7. Immunoprecipitation using anti-ACOT7 antibody estimated that 87% of enzyme activity in the homogenates was accounted for by ACOT7. On MLN sections, the germinal centers of secondary lymphoid follicles were immunostained with the antibody. In MLNs of mice fasted for 16 h, ACOT7 levels were induced 1.8-fold, which reflected a 1.5-fold increase in enzyme activity. These findings suggest that ACOT7 may be involved in dietary intake-associated responses in fatty acid metabolism in MLNs.Key words acyl-CoA thioesterase; acyl-CoA thioesterase 7; mesenteric lymph node; visceral fat Acyl-CoA thioesterases (ACOTs) comprise a group of enzymes that catalyze the hydrolysis of fatty acyl-CoA thioesters to corresponding free fatty acids and CoA. To date, 15 mammalian genes have been identified as ACOT family members.1-4) While ACOTs have the potential to regulate the intracellular levels of acyl-CoAs, free fatty acids, and CoA, their physiological functions are not fully understood. However, recent gene-knockout studies on a subgroup of ACOTs revealed that they profoundly affect lipid homeostasis in association with fatty liver development, obesity, and insulin resistance.5-7) Of the ACOT family members, ACOT1 (cytosolic), ACOT2 (mitochondrial), and ACOT7 (cytosolic) have been well characterized for their enzymatic properties (see refs. 1 and 3 for a review). These ACOTs share a common feature in that their expression is markedly induced by ligands for peroxisome proliferator-activated receptor α (PPARα), a nuclear receptor that regulates lipid metabolism-related genes, including the fibrate-class of hypolipidemic drugs. Moreover, ACOT1 and ACOT2 have been implicated in fatty acid catabolism, as emphasized by their upregulation in the liver and heart of fasted or high-fat diet-fed animals. [8][9][10][11] However, ACOT7 has enzyme activity two orders of magnitude higher than ACOT1 and ACOT2, and its expression is prominent in neurons of the central and peripheral nervous systems. [12][13][14] Thus, ACOT7 may have a role in cellular events other than energy metabolism, as the overexpression of ACOT7 in a macrophage cell line modified the production of prostaglandins.15) Recently, we examined the expression of ACOTs in fat tissues of rats 16,17) and unexpectedly found a significant level of acyl-Co...

Acyl-CoA Thioesterase 1 (ACOT1) Regulates PPARα to Couple Fatty Acid Flux With Oxidative Capacity During Fasting

“…Importantly, ACOT1 and ACOT2 are 93.7% homologous (24), and therefore the antibody generated for these studies recognizes both ACOT1 and ACOT2. However, ACOT2 is exclusively a mitochondrial protein (23), and previous groups have shown that ACOT2 runs below ACOT1 on SDS-PAGE gels (25). Therefore, to show the specificity of our antibody, we compared our samples to those of mitochondrial preparations from mouse liver overexpressing Acot2 (23).…”

Acyl-CoA thioesterase 7 is involved in cell cycle progression via regulation of PKCζ–p53–p21 signaling pathway

“…Among ACOT family members, ACOT1 (cytosolic), ACOT2 (mitochondrial), and ACOT7 (cytosolic) have been well characterized for their enzymatic properties. 4 These ACOTs share a common feature in that their expression is markedly induced by ligands for peroxisome proliferator-activated receptor α (PPAR α ), a nuclear receptor that regulates lipid metabolism-related genes such as the fibrate class of hypolipidemic drugs. 4 Moreover, ACOT1 and ACOT2 have been implicated in fatty acid catabolism, as emphasized by their upregulation in the liver and heart of fasted or high-fat-diet fed animals.…”

“… 4 These ACOTs share a common feature in that their expression is markedly induced by ligands for peroxisome proliferator-activated receptor α (PPAR α ), a nuclear receptor that regulates lipid metabolism-related genes such as the fibrate class of hypolipidemic drugs. 4 Moreover, ACOT1 and ACOT2 have been implicated in fatty acid catabolism, as emphasized by their upregulation in the liver and heart of fasted or high-fat-diet fed animals. 47 , 48 , 49 , 50 However, ACOT7 has two orders of magnitude higher enzyme activity than ACOT1 and ACOT2, and its expression is prominent in neurons of the central and peripheral nervous systems.…”

“…ACOTs have various chain length specificities on fatty acyl-CoAs and are distributed across a wide range of mammalian tissues. 2 , 3 , 4 To date, 13 mammalian genes have been identified as ACOT superfamily members, 2 , 3 , 5 and they are highly regulated by peroxisome proliferator-activated receptors (PPARs) and other nutritional factors. 1 Although their physiological functions remain incompletely understood, recent gene knockout and in-depth characterization studies have revealed that a subgroup of ACOTs profoundly affect lipid metabolism and cellular signaling.…”

“… 1 Although their physiological functions remain incompletely understood, recent gene knockout and in-depth characterization studies have revealed that a subgroup of ACOTs profoundly affect lipid metabolism and cellular signaling. 4 , 6 , 7 , 8 , 9 ACOTs are broadly grouped into two classes based on enzyme molecular weight. 2 Despite catalyzing the same reaction, these two classes are not structurally similar and do not share sequence homology.…”