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PI(4,5)P2
Phosphatidylinositol 4,5-bisphosphate or PtdIns(4,5)''P''2, also known simply as PIP2 or PI(4,5)P2, is a minor phospholipid component of cell membranes. PtdIns(4,5)''P''2 is enriched at the plasma membrane where it is a substrate for a number of important signaling proteins. PIP2 also forms lipid clusters that sort proteins. PIP2 is formed primarily by the type I phosphatidylinositol 4-phosphate 5-kinases from PI(4)P. In metazoans, PIP2 can also be formed by type II phosphatidylinositol 5-phosphate 4-kinases from PI(5)P. The fatty acids of PIP2 are variable in different species and tissues, but the most common fatty acids are stearic in position 1 and arachidonic in 2. Signaling pathways PIP2 is a part of many cellular signaling pathways, including PIP2 cycle, PI3K signalling, and PI5P metabolism. Recently, it has been found in the nucleus with unknown function. Functions Cytoskeleton dynamics near membranes PIP2 regulates the organization, polymerization, and branc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PI(4,5)P2 Cycle
The PI(4,5)P2 cycle or simply PIP2 cycle (also known as PI cycle in past) is one of the important signalling cascades underlying many cellular functions including GPCR signaling, cytokinesis, endocytosis, and apoptosis. Signalling steps PIP2 cycle involves steps of chemical reactions characterized by various enzymes. First hydrolysis of PIP2 molecules by activated phospholipase C leads to formation of diacylglycerol and inositol trisphosphate. These two are themselves important second messengers. Diacylglycerol further converted into phosphatidic acid Phosphatidic acids are anionic phospholipids important to cell signaling and direct activation of lipid-gated ion channels. Hydrolysis of phosphatidic acid gives rise to one molecule each of glycerol and phosphoric acid and two molecules of fatty ac ... (PA) by DAGK enzyme. Furthermore, CDP-diacylglycerol synthetase uses CTP to create cytidine diphosphate diacylglycerol from PA. Generated CDP-DAG then condensed to PI by phosphat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phospholipid
Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typically have omega-3 fatty acids EPA and DHA integrated as part of the phospholipid molecule. The phosphate group can be modified with simple organic molecules such as choline, ethanolamine or serine. Phospholipids are a key component of all cell membranes. They can form lipid bilayers because of their amphiphilic characteristic. In eukaryotes, cell membranes also contain another class of lipid, sterol, interspersed among the phospholipids. The combination provides fluidity in two dimensions combined with mechanical strength against rupture. Purified phospholipids are produced commercially and have found applications in nanotechnology and materials science. The first phospholipid identified in 1847 as such in biological tissues was lecith ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
M Current
M current is a type of noninactivating potassium current first discovered in bullfrog sympathetic ganglion cells. The ''M-channel'' is a voltage-gated K+ channel ( Kv7/KCNQ family) that is named after the receptor it is influenced by. The M-channel is important in raising the threshold for firing an action potential. It is unique because it is open at rest and even more likely to be open during depolarization. Furthermore, when the muscarinic acetylcholine receptor (MAChR) is activated, the channel closes. The M-channel is a PIP2-regulated ion channel. Kv7 channels have a prominent expression throughout the brain. Function Actions of M-currents: "phasic-firing" M-channels are the reason for slow depolarizations produced by ACh and LHRH in the autonomic ganglia and other specified areas. 1. Initial depolarization of a neuron increases likelihood that M-channels will open. 2. M-channels generate an outward potassium current (IK). 3. Potassium efflux counteracts sodium influx in a ... [...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] |
Growth Hormone-releasing Hormone
Growth may refer to: Biology * Auxology, the study of all aspects of human physical growth * Bacterial growth * Cell growth * Growth hormone, a peptide hormone that stimulates growth * Human development (biology) * Plant growth * Secondary growth, growth that thickens woody plants Economics * Economic growth, the increase in the inflation-adjusted market value of the goods and services * Growth investing, a style of investment strategy focused on capital appreciation Mathematics * Exponential growth, also called geometric growth * Hyperbolic growth * Linear growth, refers to two distinct but related notions * Logistic growth, characterized as an S curve Social science * Developmental psychology * Erikson's stages of psychosocial development * Human development (humanity) * Personal development * Population growth Other uses * ''Growth'' (film), a 2010 American horror film * Izaugsme (''Growth''), a Latvian political party * ''Grown'' (album), by 2PM See also * Grow (disambi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Channel
Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na+) through a cell's membrane. They belong to the superfamily of cation channels and can be classified according to the trigger that opens the channel for such ions, i.e. either a voltage-change ("voltage-gated", "voltage-sensitive", or "voltage-dependent" sodium channel; also called "VGSCs" or "Nav channel") or a binding of a substance (a ligand) to the channel (ligand-gated sodium channels). In excitable cells such as neurons, myocytes, and certain types of glia, sodium channels are responsible for the rising phase of action potentials. These channels go through three different states called resting, active and inactive states. Even though the resting and inactive states would not allow the ions to flow through the channels the difference exists with respect to their structural conformation. Selectivity Sodium channels are highly selective for the transport of ions across cell membr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bruton's Tyrosine Kinase
Bruton's tyrosine kinase (abbreviated Btk or BTK), also known as tyrosine-protein kinase BTK, is a tyrosine kinase that is encoded by the ''BTK'' gene in humans. BTK plays a crucial role in B cell development. Structure BTK contains five different protein interaction domains. These domains include an amino terminal pleckstrin homology (PH) domain, a proline-rich TEC homology (TH) domain, SRC homology (SH) domains SH2 and SH3, as well as a kinase domain with enzymatic activity. Function BTK plays a crucial role in B cell development as it is required for transmitting signals from the pre-B cell receptor that forms after successful immunoglobulin heavy chain rearrangement. It also has a role in mast cell activation through the high-affinity IgE receptor. Btk contains a PH domain that binds phosphatidylinositol (3,4,5)-trisphosphate (PIP3). PIP3 binding induces Btk to phosphorylate phospholipase C, which in turn hydrolyzes PIP2, a phosphatidylinositol, into two second mess ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PDPK1
In the field of biochemistry, PDPK1 refers to the protein 3-phosphoinositide-dependent protein kinase-1, an enzyme which is encoded by the ''PDPK1'' gene in humans. It is implicated in the development and progression of melanomas. Function PDPK1 is a master kinase, which is crucial for the activation of AKT/PKB and many other AGC kinases including PKC, S6K, SGK. An important role for PDPK1 is in the signalling pathways activated by several growth factors and hormones including insulin signaling. Mice lacking PDPK1 die during early embryonic development, indicating that this enzyme is critical for transmitting the growth-promoting signals necessary for normal mammalian development. Mice that are deficient in PDPK1 have a ≈40% decrease in body mass, mild glucose intolerance, and are resistant to cancer brought about by hyperactivation of the PI3K pathway (PTEN+/-). Plant PDK1 plays an important role in regulating PIN-mediated auxin transport, and is thus involved in vario ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Kinase B
Protein kinase B (PKB), also known as Akt, is the collective name of a set of three serine/threonine-specific protein kinases that play key roles in multiple cellular processes such as glucose metabolism, apoptosis, cell proliferation, transcription, and cell migration. Family members - Isoforms There are three different genes that encode isoforms of Protein kinase B. These three genes are referred to as AKT1, AKT2, and AKT3 and encode the RAC alpha, beta, and gamma serine/threonine protein kinases respectively. The terms PKB and Akt may refer to the products of all three genes collectively, but sometimes are used to refer to PKB alpha and Akt1 alone. Akt1 is involved in cellular survival pathways, by inhibiting apoptotic processes. Akt1 is also able to induce protein synthesis pathways, and is therefore a key signaling protein in the cellular pathways that lead to skeletal muscle hypertrophy and general tissue growth. A mouse model with complete deletion of the Akt1 gene ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphatidylinositol (3,4,5)-trisphosphate
Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)''P''3), abbreviated PIP3, is the product of the class I phosphoinositide 3-kinases (PI 3-kinases) phosphorylation of phosphatidylinositol (4,5)-bisphosphate (PIP2). It is a phospholipid that resides on the plasma membrane. Discovery In 1988, Lewis C. Cantley published a paper describing the discovery of a novel type of phosphoinositide kinase with the unprecedented ability to phosphorylate the 3' position of the inositol ring resulting in the formation of phosphatidylinositol-3-phosphate (PI3P). Working independently, Alexis Traynor-Kaplan and coworkers published a paper demonstrating that a novel lipid, phosphatidylinositol 3,4,5 trisphosphate (PIP3) occurs naturally in human neutrophils with levels that increased rapidly following physiologic stimulation with chemotactic peptide. Subsequent studies demonstrated that ''in vivo'' the enzyme originally identified by Cantley's group prefers PtdIns(4,5)P2 as a substrate, pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Class I PI 3-kinases
Class I PI 3-kinases are a subgroup of the enzyme family, phosphoinositide 3-kinase that possess a common protein domain structure, substrate specificity, and method of activation. Class I PI 3-kinases are further divided into two subclasses, class IA PI 3-kinases and class IB PI 3-kinases. Class IA PI 3-kinases Class IA PI 3-kinases are activated by receptor tyrosine kinases (RTKs). There are three catalytic subunits that are classified as class IA PI 3-kinases: *p110α * p110β *p110δ There are currently five regulatory subunits that are known to associate with class IA PI 3-kinases catalytic subunits: *p85α and p85β * p55α and p55γ * p50α Class IB PI 3-kinases Class IB PI 3-kinases are activated by G-protein-coupled receptors (GPCRs). The only known class IB PI 3-kinase catalytic subunit is p110γ. There are two known regulatory subunits for p110γ: * p101 *p84/ p87PIKAP. See also * Phosphoinositide 3-kinase#Class I * Phosphoinositide 3-kinase inhibitor Phosp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endoplasmic Reticulum
The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum (RER), and smooth endoplasmic reticulum (SER). The endoplasmic reticulum is found in most eukaryotic cells and forms an interconnected network of flattened, membrane-enclosed sacs known as cisternae (in the RER), and tubular structures in the SER. The membranes of the ER are continuous with the outer nuclear membrane. The endoplasmic reticulum is not found in red blood cells, or spermatozoa. The two types of ER share many of the same proteins and engage in certain common activities such as the synthesis of certain lipids and cholesterol. Different types of cells contain different ratios of the two types of ER depending on the activities of the cell. RER is found mainly toward the nucleus of cell and SER towards the cell membrane or plasma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
