In cell physiology, a secondary messenger system (also known as a second messenger system) is a method of cellular signalling where the signalling molecule does not enter the cell, but rather utilizes a cascade of events that transduces the signal into a cellular change. Secondary messengers are a component of signal transduction cascades. Cell physiology is the study of its mechanism and interaction in its environment. ... This article or section does not cite its references or sources. ...

Secondary messenger systems utilize receptors on the surface of the plasma membrane which are generally coupled to a kinase on the interior surface of the membrane. The kinase then phosphorylates another molecule (frequently cAMP) which carries out another action. Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... In biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific target molecules (substrates); the process is termed phosphorylation. ... Structure of cAMP cAMP represented in three ways, the left with sticks-representation, the middle with structure formula, and the right with space filled representation. ...

Secondary messengers are associated with many hormones, but they are not used by steroid hormone receptors or ligand-gated ion channels. Steroid hormone receptors are generally intracellular (specifically cytoplasmatic) receptors that perform signal transduction for steroid hormones. ... Ligand-gated ion channel is a broad term that refers to any ion channel that is gated (i. ...

Types of secondary messenger molecules

There are three basic types of secondary messenger molecules:

• Hydrophobic molecules like diacylglycerol, InsP₃ and phosphatidylinositols are membrane-associated and diffuse from the plasma membrane into the juxtamembrane space where they can reach and regulate membrane-associated effector proteins.
• Hydrophilic molecules are water-soluble molecules, like cAMP, cGMP, and Ca²⁺, that are located within the cytosol.
• gases, nitric oxide (NO) and carbon monoxide (CO), that can diffuse both through cytosol and across cellular membranes.

These intracellular messengers have some properties in common: Hydrophobe (from the Greek (hydros) water and (phobos) fear) in chemistry refers to the physical property of a molecule that is repelled by water. ... Diacylglycerol (DAG) is a second messenger molecule made by phospholipase C (a membrane-bound enzyme), together with inositol triphosphate. ... Inositol triphosphate (also commonly known as inositol trisphosphate or triphosphoinositol; abbreviated InsP3 or IP3), together with diacylglycerol, is a second messenger molecule used in signal transduction in biological cells. ... Chemical structure of sn-1-stearoyl-2-arachidonoyl phosphatidylinositol Phosphatidylinositol (abbreviated PtdIns, or PI) is a minor phospholipid component of eukaryotic cell membranes. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... Hydrophile, from the Greek (hydros) water and φιλια (philia) friendship, refers to a physical property of a molecule that can transiently bond with water (H2O) through hydrogen bonding. ... Structure of cAMP Cyclic adenosine monophosphate (cAMP, cyclic AMP or 3-5-cyclic adenosine monophosphate) is a molecule that is important in many biological processes; it is derived from adenosine triphosphate (ATP). ... Cyclic guanosine monophosphate (cGMP) is a second messenger derived from GTP. Cyclic guanosine monophosphate (cGMP) is a cyclic nucleotide derived from guanosine triphosphate (GTP). ... The cytosol (cf. ... This article or section does not cite its references or sources. ... Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. ...

• They can be synthesized/released and broken down again in specific reactions by enzymes.
• Some (like Ca²⁺) can be stored in special organelles and quickly released when needed.
• Their production/release and destruction can be localized, enabling the cell to limit space and time of signal activity.

Schematic of typical animal cell, showing subcellular components. ...

Common mechanisms of secondary messenger systems

There are several different secondary messenger systems (cAMP system, phosphoinositol system and arachidonic acid system), but they all are quite similar in overall mechanism, though the substances involved in those mechanisms and effects are different.

In all of these cases a neurotransmitter binds to a membrane-spanning receptor protein molecule. The binding of the neurotransmitter to the receptor changes the receptor and causes it to expose a binding site for a "G-protein". The G-protein (named for the GDP and GTP molecules that binds to it) is bound to the inner membrane of the cell and consists of three subunits alpha, beta and gamma. The G-protein is known as the "transducer."

When the G-protein binds to the receptor, it becomes able to exchange a GDP (guanosine diphosphate) molecule on its alpha subunit for a GTP (guanosine triphosphate) molecule. Once this exchange takes place, the the alpha subunit of the G-protein transducer breaks free from the beta and gamma subunits, all parts remaining membrane-bound. The alpha subunit, now free to move along the inner membrane, eventually contacts another membrane-bound protein - the "primary effector."

The primary effector then has an action, which creates a signal that can diffuse within the cell. This signal is called the "secondary messenger." (The neurotransmitter is the first messenger.) The secondary messenger may then activate a "secondary effector" whose effects depend on the particular secondary messenger system.

Examples

Camp may mean: Gatherings of people: Campsite Temporary settlement of a band of foragers. ... Inositol Phosphate group Inositol phosphates are a group of mono- to polyphosphorylated inositols. ... Arachidonic acid (AA) is an omega-6 fatty acid 20:4(ω-6). ... Cyclic guanosine monophosphate (cGMP) is a second messenger derived from GTP. Cyclic guanosine monophosphate (cGMP) is a cyclic nucleotide derived from guanosine triphosphate (GTP). ... Chemical structure of D-Aspartic Acid, a common Amino Acid neurotransmitter. ... In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. ... Norepinephrine (INN) or noradrenaline (BAN) is a catecholamine and a phenethylamine with chemical formula C8H11NO3. ... Epinephrine Norepinephrine The adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors that are targets of the catecholamines. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... Amanita muscaria from which muscarine was isolated Acetylcholine - natural agonist of muscarinic and nicotinic receptors. ... Norepinephrine (INN) or noradrenaline (BAN) is a catecholamine and a phenethylamine with chemical formula C8H11NO3. ... Epinephrine Norepinephrine The adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors that are targets of the catecholamines. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... Amanita muscaria from which muscarine was isolated Acetylcholine - natural agonist of muscarinic and nicotinic receptors. ... This article or section does not cite its references or sources. ... The histamine receptors are a class of G-protein coupled receptors with histamine as their endogenous ligand. ... Norepinephrine A hormone (from Greek όρμή - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... Adrenocorticotropic hormone (ACTH or corticotropin) is a polypeptide hormone produced and secreted by the pituitary gland. ... Atrial natriuretic factor (ANF), or atrial natriuretic peptide (ANP), is a peptide hormone that is released by walls of the cardiac atrium in response to high NaCl concentration, high extracellular fluid volume, or high blood volume. ... Corticotropin-releasing hormone (CRH), also called corticotropin-releasing factor (CRF) or corticoliberin, is a polypeptide hormone involved in the stress response. ... Calcitonin is a 32 amino acid polypeptide hormone that is produced in humans primarily by the C cells of the thyroid, and in many other animals in the ultimobranchial body. ... Follicle stimulating hormone Follicle stimulating hormone (FSH) is a hormone synthesised and secreted by gonadotropes in the anterior pituitary gland. ... Glucagon ball and stick model A microscopic image stained for glucagon. ... Human chorionic gonadotropin (hCG) is a peptide hormone produced in pregnancy, that is made by the embryo soon after conception and later by the syncytiotrophoblast (part of the placenta). ... Luteinizing hormone (LH) is a hormone synthesized and secreted by gonadotropes in the anterior lobe of the pituitary gland. ... Melanocyte-stimulating hormone (MSH) is a peptide hormone produced by cells in the intermediate lobe of the pituitary gland. ... Parathyroid hormone (PTH) is secreted by the parathyroid glands as a polypeptide containing 84 amino acids. ... Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland which regulates the endocrine function of the thyroid gland. ... Angiotensin is an oligopeptide in the blood that causes vasoconstriction, increased blood pressure, and release of aldosterone from the adrenal cortex. ... Gonadotropin-releasing hormone 1 (GNRH1 also called LHRH) is a peptide hormone responsible for the release of FSH and LH from the anterior pituitary. ... Growth hormone-releasing hormone is a hormone released from the arcuate nucleus of hypothalamus that stimulates the release of growth hormone. ... Oxytocin should not be confused with oxycodone hydrochloride whose trade name is OxyContin. ... Thyrotropin-releasing hormone (TRH), also called thyrotropin-releasing factor (TRF) or protirelin, is a tripeptide hormone that stimulates the release of thyroid-stimulating hormone and prolactin by the anterior pituitary. ... Atrial natriuretic factor (ANF), atrial natriuretic peptide (ANP) or atriopeptin, is a polypeptide hormone involved in the homeostatic control of body water and sodium. ... Insulin (from Latin insula, island, as it is produced in the Islets of Langerhans in the pancreas) is a polypeptide hormone that regulates carbohydrate metabolism. ... The insulin-like growth factors (IGFs) are polypeptides with high sequence similarity to insulin. ... This article or section does not cite its references or sources. ... This heterotrimeric G protein is illustrated with its theoretical lipid anchors. ... This heterotrimeric G protein is illustrated with its theoretical lipid anchors. ... This heterotrimeric G protein is illustrated with its theoretical lipid anchors. ... G-proteins, short for guanine nucleotide binding proteins, are a family of proteins involved in second messenger cascades. ... An effector is a small molecule that binds to a protein and thereby alters the activity of that protein. ... Adenylate cyclase (EC 4. ... Phospholipase C is a key enzyme in phosphatidylinositol (PIP2) metabolism and lipid signaling pathways. ... Phospholipases A2 (PLA2s) (PDB 1CJY, EC 3. ... Guanylate cyclase (EC 4. ... The receptor tyrosine kinase (RTK) family of cell surface receptors shows a high affinity to numerous growth signals. ... Structure of cAMP cAMP represented in three ways, the left with sticks-representation, the middle with structure formula, and the right with space filled representation. ... Inositol trisphosphate or inositol 1,4,5-trisphosphate (also commonly known as triphosphoinositol; abbreviated InsP3 or IP3), together with diacylglycerol, is a second messenger molecule used in signal transduction in biological cells. ... Diacylglycerol (DAG) is a second messenger molecule made by phospholipase C (a membrane-bound enzyme), together with inositol triphosphate. ... Chemical structure of sn-1-stearoyl-2-arachidonoyl phosphatidylinositol 4,5-bisphosphate Phosphatidylinositol (4,5)-bisphosphate (PtdIns(4,5)P2) is a minor phospholipid component of cell membranes. ... Arachidonic acid (AA) is an omega-6 fatty acid 20:4(ω-6). ... Cyclic guanosine monophosphate (cGMP) is a second messenger derived from GTP. Cyclic guanosine monophosphate (cGMP) is a cyclic nucleotide derived from guanosine triphosphate (GTP). ... In cell biology, cAMP-dependent protein kinase (cAPK), also known as protein kinase A (PKA)(EC 2. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... Calcium-binding proteins are proteins that participate in calcium cell signalling pathways by binding to Ca2+. The most ubiquitous Ca2+-sensing protein, found in all eukaryotic organisms including yeasts, is calmodulin. ... A protein kinase is an enzyme that can transfer a phosphate group from a donor molecule (usually ATP) to an amino acid residue of a protein. ... Lipoxygenases are iron-containing enzymes that catalyse the dioxygenation of polyunsaturated fatty acids in reaction: fatty acid + O2 = fatty acid hydroperoxide Lipoxygenases are found in plants and in animals. ... Lipoxygenases are iron-containing enzymes that catalyse the dioxygenation of polyunsaturated fatty acids in reaction: fatty acid + O2 = fatty acid hydroperoxide Lipoxygenases are found in plants and in animals. ... Enzyme cyclooxygenase (box: first step in creating prostaglandins from fatty acids) (more details. ... Protein Kinase G (PKG) is enzyme that catalyzes the transfer of phosphate from ATP? to hydroxyl side chains on proteins, causing changes in function. ...

External links

• MeSH Second+Messenger+Systems
• Kimball, J. Second messengers. Retrieved on February 10, 2006.