AKT/PKB Signaling Pathway | PI3k Signaling

Hussain Biology
Hussain Biology
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Published 2020-06-10
This video will be encompass the AKT/PKB Signaling Pathway .
The Akt Pathway, or PI3K-Akt Pathway is a signal transduction pathway that promotes survival and growth in response to extracellular signals. Key proteins involved are PI3K (phosphatidylinositol 3-kinase) and Akt (Protein Kinase B).
Initial stimulation by one of the growth factors causes activation of a cell surface receptor and phosphorylation of PI3K. Activated PI3K then phosphorylates lipids on the plasma membrane, forming second messenger phosphatidylinositol (3,4,5)-trisphosphate (PIP3). Akt, a serine/threonine kinase, is recruited to the membrane by interaction with these phosphoinositide docking sites, so that it can be fully activated.[1] Activated Akt mediates downstream responses, including cell survival, growth, proliferation, cell migration and angiogenesis, by phosphorylating a range of intracellular proteins. The pathway is present in all cells of higher eukaryotes and is highly conserved.
There are multiple types of phosphoinositide 3-kinase but only class I are responsible for lipid phosphorylation in response to growth stimuli.
Akt resides in the cytosol in an inactive conformation, until the cell is stimulated and it translocates to the plasma membrane. The Akt PH domain has a high affinity for second messenger PI(3,4,5)P3, binding to it preferentially over other phosphoinositides.[11] Thus PI3K activity is essential for translocation of Akt to the membrane. Interaction with PI(3,4,5)P3 causes conformational changes and exposure of phosphorylation sites Thr308 in the kinase domain and Ser473 in the C-terminal domain. Akt is partially activated by phosphorylation of T308 by PDK1. Full activation requires phosphorylation of S473, which can be catalysed by multiple proteins, including phosphoinositide-dependent kinase 2 (PDK2), integrin-linked kinase (ILK)
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