Metabotropy
A metabotropic receptor is a cell membrane - receptor . The main difference to the ionotropic receptor is that another signal cascade , the second messenger path, follows on the intracellular side of the receptor . This division of the signal cascade leads to considerably longer reaction times, which can go up to seconds. Therefore, the metabotropic receptors are slow receptors.
Metabotropic receptors therefore have no direct influence on the ionic ratios and currents and thus on the membrane potential . Most of the water-soluble hormones and many transmitters in the nervous system use such receptors.
When a distinction is second messenger - signaling between G-protein-coupled receptors and enzyme-coupled receptors .
G protein coupled receptors
- Main article: G-protein coupled receptor
In the case of G protein-coupled receptors, the signal is coupled via a G protein on the intracellular side. Depending on the receptor and G protein type, this can lead to activation of the IP 3 / DAG pathway or to an increase or decrease in the cAMP level.
Examples are the adrenoreceptors , represented by catecholamines are activated (ie, epinephrine and norepinephrine) and the muscarinic acetylcholine receptor.
The second messenger then leads to the desired effect in the cell, for example to an influx of calcium in the IP3 / DAG path and thus to a contraction of a (smooth) muscle cell or in the cAMP path to switching it on and off ( Interconversion) of enzymes.
Enzyme-Coupled Receptors
- Main article: Enzyme-coupled receptor
A common variant leads to an autophosphorylation of tyrosine residues on the intracellular side of the receptor (for example the insulin receptor) and thus to signal transmission.
literature
- G. Chaldakov: The metabotropic NGF and BDNF: an emerging concept. In: Archives Italiennes de Biologie. Volume 149, Number 2, June 2011, pp. 257-263, ISSN 0003-9829 . PMID 21701997 .