The mitochondrial dicarboxylate carrier (DIC) is an integral membrane protein encoded by the SLC25A10 gene in humans that catalyzes the transport of dicarboxylates such as malonate, malate, and succinate across the inner mitochondrial membrane in exchange for phosphate, sulfate, and thiosulfate by a simultaneous antiport mechanism, thus supplying substrates for the Krebs cycle, gluconeogenesis, urea synthesis, fatty acid synthesis, and sulfur metabolism. [4] [5] [6] [7] [8]
The SLC25A10 gene is located on the q arm of chromosome 17 in position 25.3 and spans 8,781 base pairs. [7] The gene has 11 exons and produces a 31.3 kDa protein composed of 287 amino acids. [9] [10] Intron 1 of this gene has five short Alu sequences. [11] [12] Mitochondrial dicarboxylate carriers are dimers, each consisting of six transmembrane domains with both the N- and C- terminus exposed to the cytoplasm. [13] Like all mitochondrial carriers, dicarboxylate carriers features a tripartite structure with three repeats of about 100 amino acid residues, each of which contains a conserved sequence motif. [14] These three tandem sequences fold into two anti-parallel transmembrane α-helices linked by hydrophilic sequences. [5]
A crucial function of dicarboxylate carriers is to export malate from the mitochondria in exchange for inorganic phosphate. Dicarboxylate carriers are highly abundant in the adipose tissue and play a central role in supplying cytosolic malate for the citrate transporter, which then exchanges cytosolic malate for mitochondrial citrate to begin fatty acid synthesis. [15] Abundant levels of DIC are also detected in the kidneys and liver, whereas lower levels are found in the lung, spleen, heart, and brain. [11] Dicarboxylate carriers are involved in glucose-stimulated insulin secretion through pyruvate cycling, which mediates NADPH production, and by providing cytosolic malate as a counter-substrate for citrate export. [16] It is also involved in reactive oxygen species (ROS) production through hyperpolarization of mitochondria and increases ROS levels when overexpressed. [17] Furthermore, dicarboxylate carriers are crucial for cellular respiration, and inhibition of DIC impairs complex I activity in mitochondria. [18]
Insulin causes a dramatic (approximately 80%) reduction of DIC expression in mice, whereas free fatty acids induces DIC expression. Cold exposure, which increases energy expenditure and decreases fatty acid biosynthesis, resulted in a significant (approximately 50%) reduction of DIC expression. [13] DIC is inhibited by some dicarboxylate analogues, such as butylmalonate, as well as bathophenanthroline and thiol reagents such as Mersalyl and p-hydroxymercuribenzoate. [19] [20] [21] The activity of dicarboxylate carriers has also been found to be upregulated in plants in response to stress. [22] The rate of malonate uptake is inhibited by 2-oxoglutarate and unaffected by citrate, whereas the rates of succinate and malate uptake are inhibited by both 2-oxoglutarate and citrate.
Suppression of SLC25A10 down-regulated fatty acid synthesis in mice, resulting in decreased lipid accumulation in adipocytes. Additionally, knockout of SLC25A10 inhibited insulin-stimulated lipogenesis in adipocytes. These findings presents a possible target for anti-obesity treatments. [15] [23] It is also upregulated in tumors, which is likely because it regulates energy metabolism and redox homeostasis, both of which are frequently altered in tumor cells. In non-small cell lung cancer (NSCLC) cells, inhibition of SLC25A10 was found to increase the sensitivity to traditional anticancer drugs, and thus may present a potential target for anti-cancer strategies. [24] Furthermore, overexpression of dicarboxylate carriers in renal proximal tubular cells has been found to cause a reversion to a non-diabetic state and protect cells from oxidative injury. This finding supports the dicarboxylate carriers as a potential therapeutic target to correct underlying metabolic disturbances in diabetic nephropathy. [25]
This protein has binary interactions with NOTCH2NL, KRTAP5-9, KRTAP4-2, KRTAP10-8, MDFI, and KRT40. [26] [27]
The citric acid cycle (CAC) – also known as the TCA cycle or the Krebs cycle – is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. The TCA cycle is used by organisms that respire to generate energy, either by anaerobic respiration or aerobic respiration. In addition, the cycle provides precursors of certain amino acids, as well as the reducing agent NADH, that are used in numerous other reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest components of metabolism and may have originated abiogenically. Even though it is branded as a 'cycle', it is not necessary for metabolites to follow only one specific route; at least three alternative segments of the citric acid cycle have been recognized.
Thermogenin is a mitochondrial carrier protein found in brown adipose tissue (BAT). It is used to generate heat by non-shivering thermogenesis, and makes a quantitatively important contribution to countering heat loss in babies which would otherwise occur due to their high surface area-volume ratio.
Mitochondrial carriers are proteins from solute carrier family 25 which transfer molecules across the membranes of the mitochondria. Mitochondrial carriers are also classified in the Transporter Classification Database. The Mitochondrial Carrier (MC) Superfamily has been expanded to include both the original Mitochondrial Carrier (MC) family and the Mitochondrial Inner/Outer Membrane Fusion (MMF) family.
Aspartate aminotransferase, mitochondrial is an enzyme that in humans is encoded by the GOT2 gene. Glutamic-oxaloacetic transaminase is a pyridoxal phosphate-dependent enzyme which exists in cytoplasmic and inner-membrane mitochondrial forms, GOT1 and GOT2, respectively. GOT plays a role in amino acid metabolism and the urea and tricarboxylic acid cycles. Also, GOT2 is a major participant in the malate-aspartate shuttle, which is a passage from the cytosol to the mitochondria. The two enzymes are homodimeric and show close homology. GOT2 has been seen to have a role in cell proliferation, especially in terms of tumor growth.
Phosphate carrier protein, mitochondrial is a protein that in humans is encoded by the SLC25A3 gene. The encoded protein is a transmembrane protein located in the mitochondrial inner membrane and catalyzes the transport of phosphate ions across it for the purpose of oxidative phosphorylation. There are two significant isoforms of this gene expressed in human cells, which differ slightly in structure and function. Mutations in this gene can cause mitochondrial phosphate carrier deficiency (MPCD), a fatal disorder of oxidative phosphorylation symptomized by lactic acidosis, neonatal hypotonia, hypertrophic cardiomyopathy, and death within the first year of life.
Mitochondrial 2-oxoglutarate/malate carrier protein is a protein that in humans is encoded by the SLC25A11 gene. Inactivating mutations in this gene predispose to metastasic paraganglioma.
Very long-chain acyl-CoA synthetase is an enzyme that in humans is encoded by the SLC27A2 gene.
Mitochondrial thiamine pyrophosphate carrier is a protein that in humans is encoded by the SLC25A19 gene.
Calcium-binding mitochondrial carrier protein Aralar1 is a protein that in humans is encoded by the SLC25A12 gene. Aralar is an integral membrane protein located in the inner mitochondrial membrane. Its primary function as an antiporter is the transport of cytoplasmic glutamate with mitochondrial aspartate across the inner mitochondrial membrane, dependent on the binding of one calcium ion. Mutations in this gene cause early infantile epileptic encephalopathy 39 (EIEE39), symptomized by global hypomyelination of the central nervous system, refractory seizures, and neurodevelopmental impairment. This gene has connections to autism.
Solute carrier family 13 member 2 is a protein that is encoded in humans by the SLC13A2 gene.
Long-chain fatty acid transport protein 6 is a protein that in humans is encoded by the SLC27A6 gene.
Tricarboxylate transport protein, mitochondrial, also known as tricarboxylate carrier protein and citrate transport protein (CTP), is a protein that in humans is encoded by the SLC25A1 gene. SLC25A1 belongs to the mitochondrial carrier gene family SLC25. High levels of the tricarboxylate transport protein are found in the liver, pancreas and kidney. Lower or no levels are present in the brain, heart, skeletal muscle, placenta and lung.
ADP/ATP translocase 4 (ANT4) is an enzyme that in humans is encoded by the SLC25A31 gene on chromosome 4. This enzyme inhibits apoptosis by catalyzing ADP/ATP exchange across the mitochondrial membranes and regulating membrane potential. In particular, ANT4 is essential to spermatogenesis, as it imports ATP into sperm mitochondria to support their development and survival. Outside this role, the SLC25AC31 gene has not been implicated in any human disease.
ADP/ATP translocase 3, also known as solute carrier family 25 member 6, is a protein that in humans is encoded by the SLC25A6 gene.
The organic anion transporter 1 (OAT1) also known as solute carrier family 22 member 6 (SLC22A6) is a protein that in humans is encoded by the SLC22A6 gene. It is a member of the organic anion transporter (OAT) family of proteins. OAT1 is a transmembrane protein that is expressed in the brain, the placenta, the eyes, smooth muscles, and the basolateral membrane of proximal tubular cells of the kidneys. It plays a central role in renal organic anion transport. Along with OAT3, OAT1 mediates the uptake of a wide range of relatively small and hydrophilic organic anions from plasma into the cytoplasm of the proximal tubular cells of the kidneys. From there, these substrates are transported into the lumen of the nephrons of the kidneys for excretion. OAT1 homologs have been identified in rats, mice, rabbits, pigs, flounders, and nematodes.
Mitochondrial 2-oxodicarboxylate carrier also known as solute carrier family 25 member 21 (SLC25A21) is a protein that in humans is encoded by the SLC25A21 gene.
ADP/ATP translocase 2 is a protein that in humans is encoded by the SLC25A5 gene on the X chromosome.
Acyl-CoA thioesterase 9 is a protein that is encoded by the human ACOT9 gene. It is a member of the acyl-CoA thioesterase superfamily, which is a group of enzymes that hydrolyze Coenzyme A esters. There is no known function, however it has been shown to act as a long-chain thioesterase at low concentrations, and a short-chain thioesterase at high concentrations.
Calcium-binding mitochondrial carrier protein SCaMC-1 is a protein that in humans is encoded by the SLC25A24 gene.
Solute carrier family 25 member 46 is a protein that in humans is encoded by the SLC25A46 gene. This protein is a member of the SLC25 mitochondrial solute carrier family. It is a transmembrane protein located in the mitochondrial outer membrane involved in lipid transfer from the endoplasmic reticulum (ER) to mitochondria. Mutations in this gene result in neuropathy and optic atrophy.
This article incorporates text available under the CC BY 4.0 license.This article incorporates text from the United States National Library of Medicine, which is in the public domain.
