second messenger

second messenger
Biochem.
any of various intracellular chemical substances, as cyclic AMP, that transmit and amplify the messages delivered by a first messenger to specific receptors on the cell surface. Cf. first messenger.
[1960-65]

* * *

 molecule inside cells (cell) that acts to transmit signals from a receptor to a target. The term second messenger was coined upon the discovery of these substances in order to distinguish them from hormones (hormone) and other molecules that function outside the cell as “first messengers” in the transmission of biological information. Many second messenger molecules are small and therefore diffuse rapidly through the cytoplasm, enabling information to move quickly throughout the cell. As elements of signaling pathways, second messengers can serve to integrate information when multiple independent upstream inputs influence the rates of synthesis and degradation of the second messenger. In addition, second messengers can have multiple downstream targets, thereby expanding the scope of signal transmission.

      A large number of second messenger molecules have been characterized, including cyclic nucleotides (nucleotide) (e.g., cyclic adenosine monophosphate, or cAMP, and cyclic guanosine monophosphate, or cGMP), ions (ion) (e.g., Ca2+), phospholipid-derived molecules (e.g., inositol triphosphate), and even a gas, nitric oxide (NO). The calcium ion Ca2+ has a critical role in the rapid responses of neurons (neuron) and muscle cells. At rest, cells maintain a low concentration of Ca2+ in the cytoplasm, expending energy to pump these ions out of the cell. When activated, neurons and muscle cells rapidly increase their cytoplasmic Ca2+ concentration by opening channels in the cell membrane (cell), which allow Ca2+ ions outside the cell to enter rapidly.

      The cyclic nucleotide cAMP is synthesized by adenylyl cyclase enzymes (enzyme), which are downstream of heterotrimeric G-proteins ( guanine nucleotide binding proteins) and receptors. For example, when epinephrine (epinephrine and norepinephrine) binds to beta-adrenergic receptors in cell membranes, G-protein activation stimulates cAMP synthesis by adenylyl cyclase. The newly synthesized cAMP is then able to act as a second messenger, rapidly propagating the epinephrine signal to the appropriate molecules in the cell. This stimulatory signaling pathway leads to the production of effects such as increasing rate and force of contraction of the heart that are characteristic of epinephrine. caffeine also enhances the action of cAMP by inhibiting the enzyme phosphodiesterase, which degrades cAMP; the enhancement of cAMP activity contributes to the general stimulatory action of caffeine. As a gas, nitric oxide (NO) is distinct among second messengers in being able to diffuse across cell membranes, which allows signal information to cross into neighbouring cells.

John A. Cooper
 

* * *


Universalium. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • Second Messenger — ist ein englischer Fachterminus der Biologie und Medizin, den man mit sekundärer Botenstoff ins Deutsche übersetzen kann. Auch sekundärer Messenger oder Sekundärsignal sind in der Fachliteratur anzutreffende, synonyme Begriffe. Ein second… …   Deutsch Wikipedia

  • second messenger — n an intracellular substance (as cyclic AMP) that mediates cell activity by relaying a signal from an extracellular molecule (as of a hormone or neurotransmitter) bound to the cell s surface compare FIRST MESSENGER * * * an organic molecule that… …   Medical dictionary

  • second messenger — second messenger. См. вторичный мессенджер. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • second messenger — second messenger, Substanzen wie z.B. cAMP, Diacylglycerin und Ca2+, die Enzymreaktionen in der Zelle bewirken und durch ⇒ Hormone, die als erste Botenstoffe Informationen übertragen, aktiviert werden …   Deutsch wörterbuch der biologie

  • Second-Messenger — Ein Second Messenger ist eine intrazelluläre chemische Substanz, deren Konzentration als Antwort auf ein Primärsignal („First Messenger“ = Ligand) verändert wird. Es dient der intrazellulären Weiterleitung eines von außen (extrazellulär)… …   Deutsch Wikipedia

  • Second messenger — Ein Second Messenger ist eine intrazelluläre chemische Substanz, deren Konzentration als Antwort auf ein Primärsignal („First Messenger“ = Ligand) verändert wird. Es dient der intrazellulären Weiterleitung eines von außen (extrazellulär)… …   Deutsch Wikipedia

  • second messenger — In many hormone sensitive systems the systemic hormone does not enter the target cell but binds to a receptor and indirectly affects the production of another molecule within the cell; this diffuses intracellularly to the target enzymes or… …   Dictionary of molecular biology

  • Second messenger system — In cell physiology, a secondary messenger system (also known as a second messenger system) is a method of cellular signaling, whereby a diffusable signaling molecule is rapidly generated/released which can then go on to activate effector proteins …   Wikipedia

  • second messenger — an organic molecule that acts within a cell to initiate the response to a signal carried by a chemical messenger (e.g. a hormone) that does not itself enter the cell. Examples of second messengers are inositol triphosphate and cyclic AMP …   The new mediacal dictionary

  • Second messenger — Вторичные посредники (second messengers, вторичные мессенджеры)  это компоненты системы передачи сигнала в клетке, малые сигнальные молекулы. Вторичные посредники являются компонентами каскадов передачи сигнала быстро образуются и далее… …   Википедия

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”