Fig. 3
From: Complex and pleiotropic signaling pathways regulated by the secreted protein augurin
Augurin modulation of the PI3K/Akt/mTOR signaling pathway. A simplified schematic representation of the PI3K/Akt/mTOR signaling pathway is shown here. Activation of growth factor receptor protein tyrosine kinases (RTKs) results in autophosphorylation on tyrosine residues. PI3K is then recruited to the membrane by directly binding to phosphotyrosine consensus residues of RTKs and activated with subsequent production of the second messenger phosphatidylinositol-3,4,5-triphosphate (PI3,4,5-P3). PI3,4,5-P3 then recruits a subset of signaling proteins, including the Akt serine/threonine kinase, which, once phosphorylated and activated, can in turn activate the mTOR serine/threonine kinase. This kinase through its downstream effectors participates to the initiation of ribosomal translation of mRNAs into proteins, ultimately regulating cell growth and cell cycle progression. Augurin has been described to negatively regulate this signaling pathway [32, 33, 45], however it is still unknown at which level of the cascade it acts, the molecular mechanisms underlying the biological effects observed remaining to be defined