Introduction
Introduction
The PI3K/Akt signaling pathway is an intracellular signaling pathway that plays an important role in apoptosis, malignancy, tumor progression, metastasis, and radiation therapy. It regulates abnormalities in cancer patients caused by mutations, amplification, deletions, methylation, and post-translational modifications. PI3K/Akt signaling pathway is often activated due to gene mutations and replication number variation (CNAs). P110α is the catalytic subunit of PI3K and is required for tumor cell proliferation, migration and invasion, while p110β is the key to cell survival and tumorigenesis. Therefore, inhibitors of PI3K and other components associated with this pathway are actively used in cancer targeted therapies.
Composition of the PI3K /Akt signaling pathway
Phosphatidylinositol 3-kinase (PI3K) is a heterodimer composed of a catalytic subunit with a molecular weight of 110 kD (p110) and a regulatory subunit with a molecular weight of 85 kD (p85). The catalytic subunit has both silk/threonine protein kinase activity and phosphatidylinositol kinase activity, which can be activated by tyrosine kinase receptors such as cytokine receptors. Akt is a downstream signaling molecule of PI3K and also has silk/threonine protein kinase activity. Its catalytically active central amino acid sequence has high sequence homology with the active centers of protein kinase A (PKA) and protein kinase C (PKC), so it is also called as PKB. The phosphorylation site during Akt activation is located in its active central domain Ser473 and Thr308. Their activation initiates downstream signaling molecules, the most important of which is the mammalian target of rapamycin (mTOR), continuing to transmit downstream signals to produce biological effects such as gene transcription, cell proliferation.
When an external signal, such as most growth factors, binds to the corresponding receptor, it will stimulate the SH2 region of the regulatory subunit binding to the phosphorylated receptor, recruiting Akt to move toward the cell membrane, while the catalytic subunit allows the cell membrane phosphatidylinositol -4, 5-bisphosphate (PIP2) phosphorylation to produce phosphatidylinositol 3,4,5-trisphosphate (PIP3). PIP3 is required for phosphoinodylinositol 3-kinase-dependent kinase (PDK) phosphorylated cell membrane Akt molecules. PDK1 directly phosphorylates Thr308 from the active center of Akt, while Ser473 phosphorylates the PDK1 - PDK2 complex, which is produced by the binding of the PH region of Akt to the lipid product. Activated Akt can act on downstream signaling molecules, such as E2F, which trigger downstream cell proliferation and differentiation cascades.
PI3K/Akt and mTOR
The PI3K /Akt /mTOR signaling pathway is located in the midstream and downstream of Akt and controls protein synthesis, angiogenesis, and cell cycle progression. mTOR, one of the important substrates of Akt, is a silk threonine kinase that has been extensively studied. Akt activates mTOR by direct or indirect pathways including direct phosphorylation of mTOR or maintaining Rheb's GTP-binding state by inactivating TSC2, and then enhance mTOR activation. This signal path exists nonlinearly due to several crosstalk and feedback adjustment mechanisms.
The PI3K/Akt signaling pathway is an intracellular signaling pathway that plays an important role in apoptosis, malignancy, tumor progression, metastasis, and radiation therapy. It regulates abnormalities in cancer patients caused by mutations, amplification, deletions, methylation, and post-translational modifications. PI3K/Akt signaling pathway is often activated due to gene mutations and replication number variation (CNAs). P110α is the catalytic subunit of PI3K and is required for tumor cell proliferation, migration and invasion, while p110β is the key to cell survival and tumorigenesis. Therefore, inhibitors of PI3K and other components associated with this pathway are actively used in cancer targeted therapies.
Composition of the PI3K /Akt signaling pathway
Phosphatidylinositol 3-kinase (PI3K) is a heterodimer composed of a catalytic subunit with a molecular weight of 110 kD (p110) and a regulatory subunit with a molecular weight of 85 kD (p85). The catalytic subunit has both silk/threonine protein kinase activity and phosphatidylinositol kinase activity, which can be activated by tyrosine kinase receptors such as cytokine receptors. Akt is a downstream signaling molecule of PI3K and also has silk/threonine protein kinase activity. Its catalytically active central amino acid sequence has high sequence homology with the active centers of protein kinase A (PKA) and protein kinase C (PKC), so it is also called as PKB. The phosphorylation site during Akt activation is located in its active central domain Ser473 and Thr308. Their activation initiates downstream signaling molecules, the most important of which is the mammalian target of rapamycin (mTOR), continuing to transmit downstream signals to produce biological effects such as gene transcription, cell proliferation.
When an external signal, such as most growth factors, binds to the corresponding receptor, it will stimulate the SH2 region of the regulatory subunit binding to the phosphorylated receptor, recruiting Akt to move toward the cell membrane, while the catalytic subunit allows the cell membrane phosphatidylinositol -4, 5-bisphosphate (PIP2) phosphorylation to produce phosphatidylinositol 3,4,5-trisphosphate (PIP3). PIP3 is required for phosphoinodylinositol 3-kinase-dependent kinase (PDK) phosphorylated cell membrane Akt molecules. PDK1 directly phosphorylates Thr308 from the active center of Akt, while Ser473 phosphorylates the PDK1 - PDK2 complex, which is produced by the binding of the PH region of Akt to the lipid product. Activated Akt can act on downstream signaling molecules, such as E2F, which trigger downstream cell proliferation and differentiation cascades.
PI3K/Akt and mTOR
The PI3K /Akt /mTOR signaling pathway is located in the midstream and downstream of Akt and controls protein synthesis, angiogenesis, and cell cycle progression. mTOR, one of the important substrates of Akt, is a silk threonine kinase that has been extensively studied. Akt activates mTOR by direct or indirect pathways including direct phosphorylation of mTOR or maintaining Rheb's GTP-binding state by inactivating TSC2, and then enhance mTOR activation. This signal path exists nonlinearly due to several crosstalk and feedback adjustment mechanisms.
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