The PI3K Signaling Pathway

PI3K, Akt, and mTOR

Phosphatidylinositol 3-kinase (PI3K), Akt (a serine/threonine kinase also known as protein kinase B [PKB]), and mammalian target of rapamycin (mTOR) are 3 major junctions in the PI3K pathway, and are typically activated by upstream signaling of tyrosine kinases and other receptor molecules.1

Class IA PI3Ks are a subgroup of the PI3K family. They are activated by receptor tyrosine kinases (RTKs) and their primary role is to convert PIP2 to PIP3. Akt is activated following recruitment to the cell surface by PIP3, and acts downstream of PI3K to regulate many cellular processes, including cell survival, proliferation, and growth.1 mTOR is a key protein in the pathway that acts both upstream and downstream of Akt.2 mTOR is active in 2 different multiprotein complexes, TORC1 and TORC2, and regulates the protein synthesis necessary for cell growth, proliferation, angiogenesis, and other cellular endpoints.3-5

The PI3K signaling pathway regulates cell survival and proliferation.1

PI3K signaling pathway image


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