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KCNJ11
Kir6.2 is a major subunit of the ATP-sensitive K+ channel, a lipid-gated inward-rectifier potassium ion channel. The gene encoding the channel is called KCNJ11 and mutations in this gene are associated with congenital hyperinsulinism. Structure It is an integral membrane protein. The protein, which has a greater tendency to allow potassium to flow into a cell rather than out of a cell, is controlled by G-proteins and is found associated with the sulfonylurea receptor (SUR) to constitute the ATP-sensitive K+ channel. Pathology Mutations in this gene are a cause of familial persistent hyperinsulinemic hypoglycemia of infancy (PHHI), an autosomal recessive disorder characterized by unregulated insulin secretion. Defects in this gene may also contribute to autosomal dominant non-insulin-dependent diabetes mellitus type II (NIDDM). See also * Inward-rectifier potassium ion channel * Potassium channel Potassium channels are the most widely distributed type of ion channel found in v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KCNJ11
Kir6.2 is a major subunit of the ATP-sensitive K+ channel, a lipid-gated inward-rectifier potassium ion channel. The gene encoding the channel is called KCNJ11 and mutations in this gene are associated with congenital hyperinsulinism. Structure It is an integral membrane protein. The protein, which has a greater tendency to allow potassium to flow into a cell rather than out of a cell, is controlled by G-proteins and is found associated with the sulfonylurea receptor (SUR) to constitute the ATP-sensitive K+ channel. Pathology Mutations in this gene are a cause of familial persistent hyperinsulinemic hypoglycemia of infancy (PHHI), an autosomal recessive disorder characterized by unregulated insulin secretion. Defects in this gene may also contribute to autosomal dominant non-insulin-dependent diabetes mellitus type II (NIDDM). See also * Inward-rectifier potassium ion channel * Potassium channel Potassium channels are the most widely distributed type of ion channel found in v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ATP-sensitive Potassium Channel
An ATP-sensitive potassium channel (or KATP channel) is a type of potassium channel that is gated by intracellular nucleotides, ATP and ADP. ATP-sensitive potassium channels are composed of Kir6.x-type subunits and sulfonylurea receptor (SUR) subunits, along with additional components. KATP channels are found in the plasma membrane; however some may also be found on subcellular membranes. These latter classes of KATP channels can be classified as being either sarcolemmal ("sarcKATP"), mitochondrial ("mitoKATP"), or nuclear ("nucKATP"). Discovery and structure KATP channels were first identified in cardiac myocytes by the Akinori Noma group in Japan. They have also been found in pancreas where they control insulin secretion, but are in fact widely distributed in plasma membranes. SarcKATP are composed of eight protein subunits (octamer). Four of these are members of the inward-rectifier potassium ion channel family Kir6.x (either Kir6.1 or Kir6.2), while the other four ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inward-rectifier Potassium Ion Channel
Inward-rectifier potassium channels (Kir, IRK) are a specific lipid-gated subset of potassium channels. To date, seven subfamilies have been identified in various mammalian cell types, plants, and bacteria. They are activated by phosphatidylinositol 4,5-bisphosphate ( PIP2). The malfunction of the channels has been implicated in several diseases. IRK channels possess a pore domain, homologous to that of voltage-gated ion channels, and flanking transmembrane segments (TMSs). They may exist in the membrane as homo- or heterooligomers and each monomer possesses between 2 and 4 TMSs. In terms of function, these proteins transport potassium (K+), with a greater tendency for K+ uptake than K+ export. The process of inward-rectification was discovered by Denis Noble in cardiac muscle cells in 1960s and by Richard Adrian and Alan Hodgkin in 1970 in skeletal muscle cells. Overview of inward rectification A channel that is "inwardly-rectifying" is one that passes current (positive cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inward-rectifier Potassium Ion Channel
Inward-rectifier potassium channels (Kir, IRK) are a specific lipid-gated subset of potassium channels. To date, seven subfamilies have been identified in various mammalian cell types, plants, and bacteria. They are activated by phosphatidylinositol 4,5-bisphosphate ( PIP2). The malfunction of the channels has been implicated in several diseases. IRK channels possess a pore domain, homologous to that of voltage-gated ion channels, and flanking transmembrane segments (TMSs). They may exist in the membrane as homo- or heterooligomers and each monomer possesses between 2 and 4 TMSs. In terms of function, these proteins transport potassium (K+), with a greater tendency for K+ uptake than K+ export. The process of inward-rectification was discovered by Denis Noble in cardiac muscle cells in 1960s and by Richard Adrian and Alan Hodgkin in 1970 in skeletal muscle cells. Overview of inward rectification A channel that is "inwardly-rectifying" is one that passes current (positive cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lipid-gated Ion Channels
Lipid-gated ion channels are a class of ion channels whose conductance of ions through the membrane depends directly on lipids. Classically the lipids are membrane resident anionic signaling lipids that bind to the transmembrane domain on the inner leaflet of the plasma membrane with properties of a classic ligand. Other classes of lipid-gated channels include the mechanosensitive ion channels that respond to lipid tension, thickness, and hydrophobic mismatch. A lipid ligand differs from a lipid cofactor in that a ligand derives its function by dissociating from the channel while a cofactor typically derives its function by remaining bound. PIP2-gated channels Phosphatidylinositol 4,5-bisphosphate (PIP2) was the first and remains the best studied lipid to gate ion channels. PIP2 is a cell membrane lipid, and its role in gating ion channels represents a novel role for the molecule. Kir channels: PIP2 binds to and directly activates inwardly rectifying potassium channels (Kir) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a basic unit of heredity and the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and noncoding genes. During gene expression, the DNA is first copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes. Genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes (many different genes) as well as gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Congenital Hyperinsulinism
Congenital hyperinsulinism is a medical term referring to a variety of congenital disorders in which hypoglycemia is caused by excessive insulin secretion.update 2013 Congenital forms of hyperinsulinemic hypoglycemia can be transient or persistent, mild or severe. These conditions are present at birth and most become apparent in early infancy. Mild cases can be treated by frequent feedings, more severe cases can be controlled by medications that reduce insulin secretion or effects. Signs and symptoms Hypoglycemia in early infancy can cause jitteriness, lethargy, unresponsiveness, or seizures. The most severe forms may cause macrosomia in utero, producing a large birth weight, often accompanied by abnormality of the pancreas. Milder hypoglycemia in infancy causes hunger every few hours, with increasing jitteriness or lethargy. Milder forms have occasionally been detected by investigation of family members of infants with severe forms, adults with the mildest degrees of congenital ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G-protein
G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior. Their activity is regulated by factors that control their ability to bind to and hydrolyze guanosine triphosphate (GTP) to guanosine diphosphate (GDP). When they are bound to GTP, they are 'on', and, when they are bound to GDP, they are 'off'. G proteins belong to the larger group of enzymes called GTPases. There are two classes of G proteins. The first function as monomeric small GTPases (small G-proteins), while the second function as heterotrimeric G protein complexes. The latter class of complexes is made up of ''alpha'' (α), ''beta'' (β) and ''gamma'' (γ) subunits. In addition, the beta and gamma subunits can form a stable dimeric complex referred to as the beta-gamma complex . Heterotrimeric G proteins located within the cell are activa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfonylurea Receptor
In molecular biology, the sulfonylurea receptors (SUR) are membrane proteins which are the molecular targets of the sulfonylurea class of antidiabetic drugs whose mechanism of action is to promote insulin release from pancreatic beta cells. More specifically, SUR proteins are subunits of the inward-rectifier potassium ion channels Kir6.x (6.1 and 6.2). The association of four Kir6.x and four SUR subunits form an ion conducting channel commonly referred to as the KATP channel. Three forms of the sulfonylurea receptor are known, SUR1 encoded by the ''ABCC8'' gene, and SUR2A and SUR2B, which are splice variants arising from a single ''ABCC9'' gene. Function The primary function of the sulfonylurea receptor is to sense intracellular levels of the nucleotides ATP and ADP and in response facilitate the open or closing its associated Kir6.x potassium channel. Hence, the KATP channel monitors the energy balance within the cell. Depending on the tissue in which the KATP channel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Congenital Hyperinsulinism
Congenital hyperinsulinism is a medical term referring to a variety of congenital disorders in which hypoglycemia is caused by excessive insulin secretion.update 2013 Congenital forms of hyperinsulinemic hypoglycemia can be transient or persistent, mild or severe. These conditions are present at birth and most become apparent in early infancy. Mild cases can be treated by frequent feedings, more severe cases can be controlled by medications that reduce insulin secretion or effects. Signs and symptoms Hypoglycemia in early infancy can cause jitteriness, lethargy, unresponsiveness, or seizures. The most severe forms may cause macrosomia in utero, producing a large birth weight, often accompanied by abnormality of the pancreas. Milder hypoglycemia in infancy causes hunger every few hours, with increasing jitteriness or lethargy. Milder forms have occasionally been detected by investigation of family members of infants with severe forms, adults with the mildest degrees of congenital ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autosomal Dominant
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second recessive. This state of having two different variants of the same gene on each chromosome is originally caused by a mutation in one of the genes, either new (''de novo'') or inherited. The terms autosomal dominant or autosomal recessive are used to describe gene variants on non-sex chromosomes ( autosomes) and their associated traits, while those on sex chromosomes (allosomes) are termed X-linked dominant, X-linked recessive or Y-linked; these have an inheritance and presentation pattern that depends on the sex of both the parent and the child (see Sex linkage). Since there is only one copy of the Y chromosome, Y-linked traits cannot be dominant or recessive. Additionally, there are other forms of dominance such as incomplete d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-insulin-dependent Diabetes Mellitus Type II
Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by hyperglycemia, high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include polydipsia, increased thirst, polyuria, frequent urination, and unexplained weight loss. Symptoms may also include polyphagia, increased hunger, feeling tired, and Ulcer (dermatology), sores that do not heal. Often symptoms come on slowly. Long-term complications from high blood sugar include heart disease, strokes, diabetic retinopathy which can result in blindness, kidney failure, and poor blood flow in the limbs which may lead to amputations. The sudden onset of hyperosmolar hyperglycemic state may occur; however, Diabetic ketoacidosis, ketoacidosis is uncommon. Type 2 diabetes primarily occurs as a result of obesity and lack of exercise. Some people are Heredity, genetically more at risk than others. Type 2 diabetes makes up about 90% of cases of diabe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
