Second messengers


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Second messengers

Molecules used to transmit signals within cells. These molecules trigger a cascade of events by activating other cellular components. The ability of cells to respond to specific extracellular molecules, or agonists, is crucial to growth, development, and homeostasis of multicellular organisms. Signal transduction refers to the movement of a signal initiated outside the cell into the cell interior. Many agonists induce the stimulation of cell growth, differentiation, or expression of specific genes. Signal transduction pathways must, therefore, include mechanisms for the initiation of signals at the cell surface membrane (plasma membrane), as well as a mechanism by which these signals traverse the interior of the cell (cytoplasm), and induce the desired target response. The pathways involve cascades of sequential molecular activation steps that are organized into three major components: (1) a receptor that recognizes and binds agonists, (2) second messengers, or signal transducing molecules, that couple receptors to intracellular pathways, and (3) effectors or molecules responsible for the ultimate response. A central feature of all signaling cascades is that they discriminate among a variety of signals and provide a mechanism for signal amplification. See Signal transduction

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
2'3'-cGAMP acts as a second messenger during host defense and may also have roles in autoimmune or inflammatory diseases, including cancer.
Inositol plays a fundamental role in the cell in two different manners: (1) incorporated in membrane phospholipids, producing phosphoinositides upon membrane receptor stimulation [41] and (2) in form of inositolphosphoglycans (IPG) that can be located at the inner or outer side of the plasma membrane and are involved in insulin transduction signaling as second messengers [42].
The discovery by Berridge found that D--myo-inositol 1,4,5-trisphosphate([IP.sub.3]) act as a second messenger, and the fundamental cell-signal transduction mechanism has been elucidated.
The worker molecules that G-proteins target include ion channels, and cyclic adenosine monophosphate (cAMP) or phospholipase C second messenger systems.
The anthology represents a considerable update and expansion of the 1999 Lipid Second Messengers.
Metabotropic receptors: Receptors for neurotransmitters that indirectly lead to the opening of ion channels via second messengers. Binding of the neurotransmitter to the receptor activates G -proteins, which in turn induce the production of second messengers such as cyclic AMP (cAMP) that then activate kinases, ultimately resulting in the opening of ion channels in the cell's membrane.
This binding initiates a series of chemical reactions inside the cell, called the second messengers, according to Fitzgerald.
Many hormones require second messengers to effect their molecular message.
The general picture that emerges from contemporary cell and developmental biology is that essentially all cellular functions are regulated by interactive 'signal transduction' networks composed of information transfer molecules, such as G proteins, protein kinases, second messengers and transcription factors.
These channels are activated in response to stimulation of the G-protein coupled receptors that, leads to the hydrolysis of [PIP.sub.2] and generation of two key intracellular second messengers, [IP.sub.3] and DAG.
Robert McNamara is author of Second Messengers (Wesleyan UP, 1990)
The pathogen also activates host PLC upon bacterial contact, leading to the production of two second messengers, which further initiate signaling events (42).