4.5 Downstream signalling from Ras (MAPK pathway)

At least three major downstream signal cascades radiate from the Ras protein.

The activation of Raf depends upon the relocalization of Raf within the cytoplasm. Recall that Ras proteins anchored to a membrane
The MAP kinase pathway
Raf-- MEK-- Erk
Each phosphorylation cause a shift in structure that results in its functional activation
Note: Ras is not a kinase

4.6
A second pathway downstream of Ras controls inositol lipids and Akt-PKB kinase
PI3K - attaches to activated receptors via its SH2 group
- is also activated by RAS-GTP

It phosphorylates inositol-containing phospholipids

The binding of PI3K to Ras causes PI3K to become further activated, where its PI substrates are located.
PI substrates for PI3 kinase PI = PhosphatidylInositol
PI3 kinase add a phosphate group to PIP2 to give PIP3
This association of PKB with the plasma membrane and its phosphorylation results in its activation
Clearly the PI3K pathway is important in cancer

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Bless this man, he literally cleared everything