Multiple mitochondrial thioesterases have distinct tissue and substrate specificity and CoA regulation, suggesting unique functional roles

Abstract

Edited by Jeffrey E. Pessin Acyl-CoA thioesterases (Acots) hydrolyze fatty acyl-CoA esters. Acots in the mitochondrial matrix are poised to mitigate ␤-oxidation overload and maintain CoA availability. Several Acots associate with mitochondria, but whether they all localize to the matrix, are redundant, or have different roles is unresolved. Here, we compared the suborganellar localization, activity, expression, and regulation among mitochondrial Acots (Acot2,-7,-9, and-13) in mitochondria from multiple mouse tissues and from a model of Acot2 depletion. Acot7,-9, and-13 localized to the matrix, joining Acot2 that was previously shown to localize there. Mitochondria from heart, skeletal muscle, brown adipose tissue, and kidney robustly expressed Acot2,-9, and-13; Acot9 levels were substantially higher in brown adipose tissue and kidney mitochondria, as was activity for C4:0-CoA, a unique Acot9 substrate. In all tissues, Acot2 accounted for about half of the thioesterase activity for C14:0-CoA and C16:0-CoA. In contrast, liver mitochondria from fed and fasted mice expressed little Acot activity, which was confined to long-chain CoAs and due mainly to Acot7 and Acot13 activities. Matrix Acots occupied different functional niches, based on substrate specificity (Acot9 versus Acot2 and-13) and strong CoA inhibition (Acot7,-9, and-13, but not Acot2). Interpreted in the context of ␤-oxidation, CoA inhibition would prevent Acotmediated suppression of ␤-oxidation, while providing a release valve when CoA is limiting. In contrast, CoA-insensitive Acot2 could provide a constitutive siphon for long-chain fatty acyl-CoAs. These results reveal how the family of matrix Acots can mitigate ␤-oxidation overload and prevent CoA limitation. Acyl-CoA thioesterases (Acots) 2 hydrolyze acyl-CoA into CoA and an acyl chain and are classified into two families based on functional domain. Type I Acots are members of the superfamily of ␣/␤-hydrolases, are found only in mammals, and have a high degree of similarity (1). Humans and rodents possess Type I Acots residing within the cytoplasm (Acot1), mitochondria (Acot2), and peroxisomes (Acot3-6 in rodents, Acot3-4 in humans) (1). In contrast, Type II Acots (Acot7-15) share little similarity beyond a hotdog fold domain (2). Some possess StAR-related lipid transfer domains (2) or can interact with a Start domain protein (3) and are found in the cytoplasm (Acot7-14), mitochondria (Acot7-13 and Acot15), and peroxisomes (Acot8) (2). Dual localization is also possible (Acot7,-11, and-13). Type I and II Acots have a signature substrate specificity that includes saturated and unsaturated fatty acyl-CoAs of different chain lengths and, in fewer cases, other CoA esters (3-5). Acots are predicted to have high biological relevance because their substrates, acyl-CoA esters, are also substrates for other enzymes that serve major metabolic pathways, such as mitochondrial ␤-oxidation, and can serve as allosteric or covalent regulators. In fact, genetic manipulation in mice of Type I or II Acots is associated ...

The Pathophysiological Role of CoA

“…The pool of CoA-SH in the cell is replenished by the enzymes that release it from thioester compounds, e.g., citrate synthase, acyl-coenzyme A: cholesterol acyltransferase (ACAT), many acyland acetyltransferases, acyl-CoA thioesterases, fatty acid synthase (FASN), fatty acid elongase (ELOVL), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), and CPT1 (Table 2), [17][18][19][20][21].Notably, changes in the CoA-SH/acetyl-CoA ratio affect not only the regulation of energy metabolism but also the regulation of other cellular processes, such as autophagy, mitosis, and cell death [20,22].…”

“…The pool of CoA-SH in the cell is replenished by the enzymes that release it from thioester compounds, e.g., citrate synthase, acyl-coenzyme A: cholesterol acyltransferase (ACAT), many acyland acetyltransferases, acyl-CoA thioesterases, fatty acid synthase (FASN), fatty acid elongase (ELOVL), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), and CPT1 (Table 2), [17][18][19][20][21].Notably, (A) This review summarizes current knowledge of CoA-SH subcellular concentrations, the roles of CoA-SH synthesis and degradation processes and changes in the level of CoA-SH under pathological conditions, such as neurodegenerative diseases, cancer, myopathies, infectious diseases and the genetic make-up of CoA-SH genes. Finally, the beneficial effects of CoA-SH and pantethine (a dimer of the CoA precursor pantetheine) used at pharmacological doses for the treatment of hyperlipidemia are presented.…”

Quantitative Mapping of Human Hair Graying and Reversal in Relation to Life Stress

“…Five proteins were consistently upregulated between experiments 1 and 2. These include three well-defined resident mitochondrial proteins involved in lipid metabolism: CPT1A, which imports fatty acids into mitochondria 64 ; ACOT7, which hydrolyzes long-chain fatty acyl-CoA esters in the mitochondrial matrix and cytoplasm 65 ; and SOD1, which dismutates superoxide anion into hydrogen peroxide (H2O2) in the mitochondrial intermembrane space 66 . The other two proteins include the actin-depolymerizing protein cofilin-1 (CFL1) and the core glycolysis enzyme phosphoglycerate kinase 1 (PGK1) ( Figure 4C ).…”

The effect of Acot2 overexpression or downregulation on the preadipocyte differentiation in Chinese Red Steppe cattle

“…Acyl-CoA thioesterase 2 (Acot2), also known as MTE-I, PTE2 and ARTISt/p43 [20], is a member of the acyl-CoA thioesterase (Acots) family [21], and is highly expressed in the mammalian kidney, heart, liver, brain, brown adipose tissue, skeletal muscles and steroid tissues [23,24,25]. The Acot2 gene does not only promote the oxidation of the mitochondrial fatty acids in the liver [29] but it is also closely related to the adipose differentiation [30].…”

“…The acyl-CoA thioesterase 2 (Acot2), also known as MTE-I, PTE2 and ARTISt/p43 [20], is a member of the acyl-CoA thioesterase (Acots) family [21]. It is highly expressed in the mammalian kidney, heart, liver, brain, brown adipose tissue, skeletal muscles and steroid tissues [23,24,25].…”