C8. Mitogen Activated Protein Kinases
- Page ID
- 5610
It is often the case that occupied receptors activate protein kinases, which activate other protein kinases, which activate yet other protein kinases to produce phospho-proteins which may act as transcription factors. An example is the mitogen activated protein kinase (MAPK system). A mitogen is an external chemical signal that causes mitosis or cell division. Activated of transcription factors by their phosphorylation through a mitogen activated kinase is required. The sequence of events is:
- binding of external signal to membrane receptor and activation of receptor kinase
- phosphorylation of receptor kinase and interaction with an activator GTP binding protein like ras
- binding of activated G-protein to and activation of a mitogen activated protein kinase kinase kinase (MAPKKK)
- MKKK phosphorylates and activates another kinase, MAPKK
- MKK phosphorylates and activates mitogen activated protein kinase, MAPK
- MAPK phosphorylates inactive transcription factors (or other proteins) and activates them. Unfortunately (from a naming point of view) when the activated proteins are themselves protein kinase, they are called mitogen activated protein kinase activated protein kinases (MAPKAPK)
There are seven types of MAPKs, four conventional and three atypical. Four typical ones are described in the table below.
Activator GTP binding protein | Ras:GTP | |||
---|---|---|---|---|
MAPKKK or MAPK3 | Raf-1A/B c-Mos |
MEKK1-4 DLK MLK2 |
MEKK1-4 DLK MLK2 |
MEKK2/3 Tpl-2 |
MAPKK or MAPK2 | MEK1,2 | MEK4,7 | MEK3,6 | MEK5 |
MAPK or MAK | ERK1,2 | JNK1-3 | p38 | ERK5 |
MAPKAPK | RSK 1-4 MNK2 MSK 1,2 |
MK2,3 | MSK1,2 MK2,3 |
RSK1-4 |
An eventual Protein Target |
c-Jun | c-Jun |
MAP Kinase System from Cell Signaling
MAP Kinase System animation from Promega
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