GLUT2
Encyclopedia
Glucose transporter 2 also known as solute carrier family 2 (facilitated glucose transporter), member 2 (SLC2A2) is a transmembrane carrier protein
that enables passive glucose
movement across cell membrane
s. It is the principal transporter
for transfer of glucose between liver
and blood
, and for renal glucose reabsorption
. In humans, this protein is encoded by the SLC2A2 gene
.
of:
. It is a very efficient carrier for glucose
.
GLUT2 also carries glucosamine
.
In small intestine during meals GLUT2 trafficking to the brush border membrane, enhancing the capacity of glucose transport when the luminal glucose concentration goes above 30mM.
.
It has been proposed by genetics researchers in neonatal and maternal-fetal medicine at Harvard University Medical School and Beth-Israel Deaconess Hospital Medical Center that this creates a problem for drug-treated diabetic pregnancies in which glucose levels in the woman are uncontrolled, exposing her fetus to the possibility of neural tube and cardiac defects in the early-developing brain, spine, and heart. However, whilst a lack of GLUT2 adaptability is negative, it is important to remember the fact that the main result of untreated gestational diabetes
appears to cause babies to be of above-average size, which may well be an advantage that is managed very well with a healthy GLUT2 status.
Maintaining a regulated osmotic balance of sugar concentration between the blood circulation and the interstitial spaces is critical in some cases of edema
including cerebral edema
.
GLUT2 appears to be particularly important to osmoregulation
, and preventing edema
-induced stroke, transient ischemic attack
or coma
, especially when blood glucose concentration is above average. GLUT2 could reasonably referred to as the "diabetic
glucose transporter" or a "stress hyperglycemia
glucose transporter."
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
that enables passive glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
movement across cell membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
s. It is the principal transporter
Glucose transporter
Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose over a plasma membrane. Because glucose is a vital source of energy for all life these transporters are present in all phyla...
for transfer of glucose between liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
, and for renal glucose reabsorption
Renal glucose reabsorption
Renal glucose reabsorption is the part of renal physiology that deals with the retrieval of filtered glucose, preventing it from disappearing from the body through the urine....
. In humans, this protein is encoded by the SLC2A2 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
.
Tissue distribution
GLUT2 is found in cellular membranesCell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
of:
- liverLiverThe liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
- pancreatic beta cells
- hypothalamusHypothalamusThe Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
- basolateral and brush border membrane of small intestineSmall intestineThe small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
- basolateral membrane of renal tubular cells
Function
GLUT2 has high capacity for glucose but low affinity (high Km, ca. 5 mM) part of "the glucose sensor" in pancreatic β-cellsBeta cell
Beta cells are a type of cell in the pancreas located in the so-called islets of Langerhans. They make up 65-80% of the cells in the islets.-Function:...
. It is a very efficient carrier for glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
.
GLUT2 also carries glucosamine
Glucosamine
Glucosamine is an amino sugar and a prominent precursor in the biochemical synthesis of glycosylated proteins and lipids. Glucosamine is part of the structure of the polysaccharides chitosan and chitin, which compose the exoskeletons of crustaceans and other arthropods, cell walls in fungi and...
.
In small intestine during meals GLUT2 trafficking to the brush border membrane, enhancing the capacity of glucose transport when the luminal glucose concentration goes above 30mM.
Clinical significance
Defects in the SLC2A2 gene are associated with a particular type of glycogen storage disease called Fanconi-Bickel syndromeGlycogen storage disease type XI
Glycogen storage disease type XI is a form of glycogen storage disease.It is also known as "Fanconi-Bickel syndrome", for Guido Fanconi and Horst Bickel.It is associated with GLUT2....
.
It has been proposed by genetics researchers in neonatal and maternal-fetal medicine at Harvard University Medical School and Beth-Israel Deaconess Hospital Medical Center that this creates a problem for drug-treated diabetic pregnancies in which glucose levels in the woman are uncontrolled, exposing her fetus to the possibility of neural tube and cardiac defects in the early-developing brain, spine, and heart. However, whilst a lack of GLUT2 adaptability is negative, it is important to remember the fact that the main result of untreated gestational diabetes
Gestational diabetes
Gestational diabetes is a condition in which women without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy . It is widely accepted as a disease only in the United States, there is some question whether the condition is natural during pregnancy...
appears to cause babies to be of above-average size, which may well be an advantage that is managed very well with a healthy GLUT2 status.
Maintaining a regulated osmotic balance of sugar concentration between the blood circulation and the interstitial spaces is critical in some cases of edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
including cerebral edema
Cerebral edema
Cerebral edema or cerebral œdema is an excess accumulation of water in the intracellular or extracellular spaces of the brain.-Vasogenic:Due to a breakdown of tight endothelial junctions which make up the blood-brain barrier...
.
GLUT2 appears to be particularly important to osmoregulation
Osmoregulation
Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too diluted or too concentrated. Osmotic pressure is a measure of the tendency of water to move...
, and preventing edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
-induced stroke, transient ischemic attack
Transient ischemic attack
A transient ischemic attack is a transient episode of neurologic dysfunction caused by ischemia – either focal brain, spinal cord or retinal – without acute infarction...
or coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
, especially when blood glucose concentration is above average. GLUT2 could reasonably referred to as the "diabetic
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
glucose transporter" or a "stress hyperglycemia
Stress hyperglycemia
Stress hyperglycemia is a medical term referring to transient elevation of the blood glucose due to the stress of illness...
glucose transporter."