For cells is communication with the environment of essential importance, around differentiation processes, surviving or thatprogrammed cell death to coordinate (Apoptose) as well as changes of the cell shape and the cell movement. In multi-cellular organisms the extracellular information is obtained for example by ions, components of the extracellular matrix , neurotransmitter , Zytokine and hormones. This signal transduction makes finally the adjustment for the cell possible to thosecurrent conditions and needs by regularization of the cell shape and - movement, the metabolism as well as the Genexpression.
By proteins in the cell membrane (receptors) and within the cell the extracellular signal is taken up and usually passed on to one or more signal cascades.This effected via coordinated protein protein interactions and is based on signal molecules, which can to change by Konformationsänderung between at least two conditions and function in such a way as molecular switches. Protein kinases have special meaning, their specific Effektorproteine either at Tyrosin - Seitenketten in this connection (v.a. Effects on Genexpression) or at series/Threonin - Seitenketten (v.a. in the metabolic regularization) release phosphorylieren and with it the Konformationsänderung. Every now and then by signal cascades also the education is released by secondary messenger materials (Second of measuringclose), the for their part determined enzymes (among other things also) activate protein kinases. In this way that becomesPrimary signal around many orders of magnitude strengthens.
The Steroidhormon receptors represent an exception of this pattern . They pass the signal on after connection of a hormone molecule not to subordinate protein kinases, but form Homodimere, those after connection at so-called. SRE (sterol response of element) in the DNA themselves as Transkriptionsfaktoren work.
chemical mechanisms of the signal transduction
one knows meanwhile different events, which change the Konformation of a signal protein:
- Phosphorylation by Kinasen and/or. the Dephosphorylierung by Phosphatasen,
- the direct interaction between two proteins,
- the connection of the nucleotides Union of Police and GTP or cyclischer nucleotideslike cAMP and cGMP as well as
- other events as for example the connection of calcium ions and acetylating.
Signal processes become frequently only by recruiting of signal proteins into specific Zellkompartimente or by local accumulation and connection to their reaction partners (“signal complexes”) and/or. Makes possible for stand proteins (“Scaffolds”).
Important signal paths are
- Wnt signal path
- TGF signal path
- FGF signal path
- Yak STAT signal path
- Map Kinase way
- G-protein-obtained signal paths
important one biological processes, which are adjusted by signal transduction, are
- immune reaction
- sense of smell
- muscle contraction
- cell pro running ration