Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles. [§ 1]
Glycolysis and Gluconeogenesis edit
- ↑ The interactive pathway map can be edited at WikiPathways: "GlycolysisGluconeogenesis_WP534".
| glucose transporter, type 1 | |||||||||||||||||||||||||||||||||||||||||||||||||||
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| Aliases | Glu_transpt_1IPR002439erythrocyte/brain hexose facilitatorGLUT1glucose transporter-1Gtr1Glut1Glut-1Glucose Transporter Type 1 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | GeneCards: | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Glucose transporter 1 (or GLUT1), also known as solute carrier family 2, facilitated glucose transporter member 1 (SLC2A1), is a uniporter protein that in humans is encoded by the SLC2A1 gene. [1] GLUT1 facilitates the transport of glucose across the plasma membranes of mammalian cells. [2] This gene encodes a facilitative glucose transporter that is highly expressed in erythrocytes and endothelial cells, including cells of the blood–brain barrier. The encoded protein is found primarily in the cell membrane and on the cell surface, where it can also function as a receptor for human T-cell leukemia virus (HTLV) I and II. [3] GLUT1 accounts for 2 percent of the protein in the plasma membrane of erythrocytes.
Mutations in this gene can cause GLUT1 deficiency syndrome 1, GLUT1 deficiency syndrome 2, idiopathic generalized epilepsy 12, dystonia 9, and stomatin-deficient cryohydrocytosis. [4] [5]
GLUT1 was the first glucose transporter to be characterized. GLUT 1 is highly conserved. [1] GLUT 1 of humans and mice have 98% identity at the amino acid level. GLUT 1 is encoded by the SLC2 gene and is one of a family of 14 genes encoding GLUT proteins. [6]
The SLC2A1 gene is located on the p arm of chromosome 1 in position 34.2 and has 10 exons spanning 33,802 base pairs. [3] The gene produces a 54.1 kDa protein composed of 492 amino acids. [7] [8] [9] [10] It is a multi-pass protein located in the cell membrane. [4] [5] This protein lacks a signal sequence; its C-terminus, N-terminus, and the very hydrophilic domain in the protein's center are all predicted to lie on the cytoplasmic side of the cell membrane. [10] [1]
GLUT1 behaves as a Michaelis–Menten enzyme and contains 12 membrane-spanning alpha helices, each containing 20 amino acid residues. A helical wheel analysis shows that the membrane-spanning alpha-helices are amphipathic, with one side being polar and the other side hydrophobic. Six of these membrane-spanning helices are believed to bind together in the membrane to create a polar channel in the center through which glucose can traverse, with the hydrophobic regions on the outside of the channel adjacent to the fatty acid tails of the membrane.[ citation needed ]
Energy-yielding metabolism in erythrocytes depends on a constant supply of glucose from the blood plasma, where the glucose concentration is maintained at about 5mM. Glucose enters the erythrocyte by facilitated diffusion via a specific glucose transporter, at a rate of about 50,000 times greater than uncatalyzed transmembrane diffusion. The glucose transporter of erythrocytes (called GLUT1 to distinguish it from related glucose transporters in other tissues) is a type III integral protein with 12 hydrophobic segments, each of which is believed to form a membrane-spanning helix. The detailed structure of GLUT1 is not known yet, but one plausible model suggests that the side-by-side assembly of several helices produces a transmembrane channel lined with hydrophilic residues that can hydrogen-bond with glucose as it moves through the channel. [11]
GLUT1 is responsible for the low level of basal glucose uptake required to sustain respiration in all cells. Expression levels of GLUT1 in cell membranes are increased by reduced glucose levels and decreased by increased glucose levels.[ citation needed ]
GLUT1 is also a major receptor for uptake of Vitamin C as well as glucose, especially in non vitamin C producing mammals as part of an adaptation to compensate by participating in a Vitamin C recycling process. In mammals that do produce Vitamin C, GLUT4 is often expressed instead of GLUT1. [12]
GLUT1 expression occurs in almost all tissues, with the degree of expression typically correlating with the rate of cellular glucose metabolism. In the adult it is expressed at highest levels in erythrocytes and also in the endothelial cells of barrier tissues such as the blood–brain barrier. [13]
Mutations in the GLUT1 gene are responsible for GLUT1 deficiency or De Vivo disease, which is a rare autosomal dominant disorder. [14] This disease is characterized by a low cerebrospinal fluid glucose concentration (hypoglycorrhachia), a type of neuroglycopenia, which results from impaired glucose transport across the blood–brain barrier.
Many mutations in the SLC2A1 gene, including LYS456TER, TYR449TER, LYS256VAL, ARG126HIS, ARG126LEU and GLY91ASP, have been shown to cause GLUT1 deficiency syndrome 1 (GLUT1DS1), a neurologic disorder showing wide phenotypic variability. This disease can be inherited in either an autosomal recessive or autosomal dominant manner. [10] The most severe 'classic' phenotype comprises infantile-onset epileptic encephalopathy associated with delayed development, acquired microcephaly, motor incoordination, and spasticity. Onset of seizures, usually characterized by apneic episodes, staring spells, and episodic eye movements, occurs within the first 4 months of life. Other paroxysmal findings include intermittent ataxia, confusion, lethargy, sleep disturbance, and headache. Varying degrees of cognitive impairment can occur, ranging from learning disabilities to severe mental retardation. [4] [5]
Other mutations, like GLY314SER, ALA275THR, ASN34ILE, SER95ILE, ARG93TRP, ARG91TRP, a 3-bp insertion (TYR292) and a 12-bp deletion (1022_1033del) in exon 6, have been shown to cause GLUT1 deficiency syndrome 2 (GLUT1DS2), a clinically variable disorder characterized primarily by onset in childhood of paroxysmal exercise-induced dyskinesia. The dyskinesia involves transient abnormal involuntary movements, such as dystonia and choreoathetosis, induced by exercise or exertion, and affecting the exercised limbs. Some patients may also have epilepsy, most commonly childhood absence epilepsy. Mild mental retardation may also occur. In some patients involuntary exertion-induced dystonic, choreoathetotic, and ballistic movements may be associated with macrocytic hemolytic anemia. [4] [5] Inheritance of this disease is autosomal dominant. [10]
Some mutations, particularly ASN411SER, ARG458TRP, ARG223PRO and ARG232CYS, have been shown to cause idiopathic generalized epilepsy 12 (EIG12), a disorder characterized by recurring generalized seizures in the absence of detectable brain lesions and/or metabolic abnormalities. Generalized seizures arise diffusely and simultaneously from both hemispheres of the brain. Seizure types include juvenile myoclonic seizures, absence seizures, and generalized tonic-clonic seizures. In some EIG12 patients seizures may remit with age. [4] [5] Inheritance of this disease is autosomal dominant. [10]
Another mutation, ARG212CYS, has been shown to cause Dystonia 9 (DYT9), an autosomal dominant neurologic disorder characterized by childhood onset of paroxysmal choreoathetosis and progressive spastic paraplegia. Most patients show some degree of cognitive impairment. Other variable features may include seizures, migraine headaches, and ataxia. [4] [5]
Certain mutations, like GLY286ASP and a 3-bp deletion in ILE435/436, cause Stomatin-deficient cryohydrocytosis with neurologic defects (SDCHCN), a rare form of stomatocytosis characterized by episodic hemolytic anemia, cold-induced red cells cation leak, erratic hyperkalemia, neonatal hyperbilirubinemia, hepatosplenomegaly, cataracts, seizures, mental retardation, and movement disorder. [4] [5] Inheritance of this disease is autosomal dominant. [10]
GLUT1 is also a receptor used by the HTLV virus to gain entry into target cells. [15]
Glut1 has also been demonstrated as a powerful histochemical marker for hemangioma of infancy [16]
GLUT1 has been shown to interact with GIPC1. [17] It is found in a complex with Adducin (ADD2) and Dematin (EPB49) and interacts (via C-terminus cytoplasmic region) with Dematin isoform 2. [18] It also interacts with SNX27; the interaction is required when endocytosed to prevent degradation in lysosomes and promote recycling to the plasma membrane. [19] This protein interacts with STOM. [20] It interacts with SGTA (via Gln-rich region) and has binary interactions with CREB3-2. [4] [5]
GLUT1 has two significant types in the brain: 45-kDa and 55-kDa. GLUT1 45-kDa is present in astroglia and neurons. GLUT1 55-kDa is present in the endothelial cells of the brain vasculature and is responsible for glucose transport across the blood–brain barrier; its deficiency causes a low level of glucose in CSF (less than 60 mg/dl) which may elicit seizures in deficient individuals.[ citation needed ]
Recently a GLUT1 inhibitor DERL3 has been described and is often methylated in colorectal cancer. In this cancer, DERL3 methylations seem to mediate the Warburg effect. [21]
Fasentin is a small molecule inhibitor of the intracellular domain of GLUT1 preventing glucose uptake. [22]
Recently, a new more selective GLUT1 inhibitor, Bay-876, has been described. [23]
Click on genes, proteins and metabolites below to link to respective articles. [§ 1]
Mediated transport refers to transport mediated by a membrane transport protein. Substances in the human body may be hydrophobic, electrophilic, contain a positively or negatively charge, or have another property. As such there are times when those substances may not be able to pass over the cell membrane using protein-independent movement. The cell membrane is imbedded with many membrane transport proteins that allow such molecules to travel in and out of the cell. There are three types of mediated transporters: uniport, symport, and antiport. Things that can be transported are nutrients, ions, glucose, etc, all depending on the needs of the cell. One example of a uniport mediated transport protein is GLUT1. GLUT1 is a transmembrane protein, which means it spans the entire width of the cell membrane, connecting the extracellular and intracellular region. It is a uniport system because it specifically transports glucose in only one direction, down its concentration gradient across the cell membrane.
A membrane transport protein is a membrane protein involved in the movement of ions, small molecules, and macromolecules, such as another protein, across a biological membrane. Transport proteins are integral transmembrane proteins; that is they exist permanently within and span the membrane across which they transport substances. The proteins may assist in the movement of substances by facilitated diffusion, active transport, osmosis, or reverse diffusion. The two main types of proteins involved in such transport are broadly categorized as either channels or carriers. Examples of channel/carrier proteins include the GLUT 1 uniporter, sodium channels, and potassium channels. The solute carriers and atypical SLCs are secondary active or facilitative transporters in humans. Collectively membrane transporters and channels are known as the transportome. Transportomes govern cellular influx and efflux of not only ions and nutrients but drugs as well.
Uniporters, also known as solute carriers or facilitated transporters, are a type of membrane transport protein that passively transports solutes across a cell membrane. It uses facilitated diffusion for the movement of solutes down their concentration gradient from an area of high concentration to an area of low concentration. Unlike active transport, it does not require energy in the form of ATP to function. Uniporters are specialized to carry one specific ion or molecule and can be categorized as either channels or carriers. Facilitated diffusion may occur through three mechanisms: uniport, symport, or antiport. The difference between each mechanism depends on the direction of transport, in which uniport is the only transport not coupled to the transport of another solute.
Dehydroascorbic acid (DHA) is an oxidized form of ascorbic acid. It is actively imported into the endoplasmic reticulum of cells via glucose transporters. It is trapped therein by reduction back to ascorbate by glutathione and other thiols. The (free) chemical radical semidehydroascorbic acid (SDA) also belongs to the group of oxidized ascorbic acids.
Glucose transporter 2 (GLUT2) also known as solute carrier family 2, member 2 (SLC2A2) is a transmembrane carrier protein that enables protein facilitated glucose movement across cell membranes. It is the principal transporter for transfer of glucose between liver and blood Unlike GLUT4, it does not rely on insulin for facilitated diffusion.
Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose across the plasma membrane, a process known as facilitated diffusion. Because glucose is a vital source of energy for all life, these transporters are present in all phyla. The GLUT or SLC2A family are a protein family that is found in most mammalian cells. 14 GLUTS are encoded by the human genome. GLUT is a type of uniporter transporter protein.
Hereditary stomatocytosis describes a number of inherited, mostly autosomal dominant human conditions which affect the red blood cell and create the appearance of a slit-like area of central pallor (stomatocyte) among erythrocytes on peripheral blood smear. The erythrocytes' cell membranes may abnormally 'leak' sodium and/or potassium ions, causing abnormalities in cell volume. Hereditary stomatocytosis should be distinguished from acquired causes of stomatocytosis, including dilantin toxicity and alcoholism, as well as artifact from the process of preparing peripheral blood smears.
Glucose transporter type 4 (GLUT4), also known as solute carrier family 2, facilitated glucose transporter member 4, is a protein encoded, in humans, by the SLC2A4 gene. GLUT4 is the insulin-regulated glucose transporter found primarily in adipose tissues and striated muscle. The first evidence for this distinct glucose transport protein was provided by David James in 1988. The gene that encodes GLUT4 was cloned and mapped in 1989.
Method of glucose uptake differs throughout tissues depending on two factors; the metabolic needs of the tissue and availability of glucose. The two ways in which glucose uptake can take place are facilitated diffusion and secondary active transport. Active transport is the movement of ions or molecules going against the concentration gradient.
Glucose transporter 3, also known as solute carrier family 2, facilitated glucose transporter member 3 (SLC2A3) is a protein that in humans is encoded by the SLC2A3 gene. GLUT3 facilitates the transport of glucose across the plasma membranes of mammalian cells. GLUT3 is most known for its specific expression in neurons and has originally been designated as the neuronal GLUT. GLUT3 has been studied in other cell types with specific glucose requirements, including sperm, preimplantation embryos, circulating white blood cells and carcinoma cell lines.
GLUT1 deficiency syndrome, also known as GLUT1-DS, De Vivo disease or Glucose transporter type 1 deficiency syndrome, is an autosomal dominant genetic metabolic disorder associated with a deficiency of GLUT1, the protein that transports glucose across the blood brain barrier. Glucose Transporter Type 1 Deficiency Syndrome has an estimated birth incidence of 1 in 90,000 to 1 in 24,300. This birth incidence translates to an estimated prevalence of 3,000 to 7,000 in the U.S.
Thiamine transporter 1, also known as thiamine carrier 1 (TC1) or solute carrier family 19 member 2 (SLC19A2) is a protein that in humans is encoded by the SLC19A2 gene. SLC19A2 is a thiamine transporter. Mutations in this gene cause thiamine-responsive megaloblastic anemia syndrome (TRMA), which is an autosomal recessive disorder characterized by diabetes mellitus, megaloblastic anemia and sensorineural deafness.
ATP-binding cassette transporter ABCA1, also known as the cholesterol efflux regulatory protein (CERP) is a protein which in humans is encoded by the ABCA1 gene. This transporter is a major regulator of cellular cholesterol and phospholipid homeostasis.
The major facilitator superfamily (MFS) is a superfamily of membrane transport proteins that facilitate movement of small solutes across cell membranes in response to chemiosmotic gradients.
Rh-associated glycoprotein (RHAG) is an ammonia transporter protein that in humans is encoded by the RHAG gene. RHAG has also recently been designated CD241. Mutations in the RHAG gene can cause stomatocytosis.
Monocarboxylate transporter 1 is a ubiquitous protein that in humans is encoded by the SLC16A1 gene. It is a proton coupled monocarboxylate transporter.
Inborn errors of carbohydrate metabolism are inborn error of metabolism that affect the catabolism and anabolism of carbohydrates.
Paroxysmal exercise-induced dystonia or PED is a rare neurological disorder characterized by sudden, transient, involuntary movements, often including repetitive twisting motions and painful posturing triggered by exercise or other physical exertion. PED is in the class of paroxysmal dyskinesia which are a group of rare movement disorders characterized by attacks of hyperkinesia with intact consciousness. The term paroxysmal indicates that the episodes are sudden and short lived and usually unpredicted, and return to normal is rapid. The number of reported cases of people with PED is very small leading to difficulty in studying and classifying this disease and most studies are limited to a very small number of test subjects.
Solute carrier family 25 member 22 is a protein that in humans is encoded by the SLC25A22 gene. This gene encodes a mitochondrial glutamate carrier. Mutations in this gene are associated with early infantile epileptic encephalopathy. Expression of this gene is increased in colorectal tumor cells.
SLC45A1 is a member of the SLC45 family of solute carriers. Analysis of the protein function in a recombinant yeast expression assay show that it can: (i) transport a disaccharide, such as glucose and sucrose (ii) perform secondary active transport in a proton-dependent manner.
This article incorporates text from this source, which is in the public domain : "Entrez Gene: Transmembrane protein 70" . Retrieved 2018-08-14.
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.