Assuntos
Proteínas de Ciclo Celular/metabolismo , Complexos Endossomais de Distribuição Requeridos para Transporte/metabolismo , Subunidades beta da Proteína de Ligação ao GTP/metabolismo , Subunidades gama da Proteína de Ligação ao GTP/metabolismo , Cinesinas/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Proteínas Nucleares/metabolismo , Mapas de Interação de Proteínas , Fuso Acromático/metabolismo , Células HEK293 , Células HeLa , Humanos , Fuso Acromático/ultraestruturaRESUMO
Diverse G protein-coupled receptors depend on Gßγ heterodimers to promote cell polarization and survival via direct activation of PI3Kγ and potentially other effectors. These events involve full activation of AKT via its phosphorylation at Ser473, suggesting that mTORC2, the kinase that phosphorylates AKT at Ser473, is activated downstream of Gßγ. Thus, we tested the hypothesis that Gßγ directly contributes to mTOR signaling. Here, we demonstrate that endogenous mTOR interacts with Gßγ. Cell stimulation with serum modulates Gßγ interaction with mTOR. The carboxyl terminal region of mTOR, expressed as a GST-fusion protein, including the serine/threonine kinase domain, binds Gßγ heterodimers containing different Gß subunits, except Gß4. Both, mTORC1 and mTORC2 complexes interact with Gß1γ2 which promotes phosphorylation of their respective substrates, p70S6K and AKT. In addition, chronic treatment with rapamycin, a condition known to interfere with assembly of mTORC2, reduces the interaction between Gßγ and mTOR and the phosphorylation of AKT; whereas overexpression of Gαi interfered with the effect of Gßγ as promoter of p70S6K and AKT phosphorylation. Altogether, our results suggest that Gßγ positively regulates mTOR signaling via direct interactions and provide further support to emerging strategies based on the therapeutical potential of inhibiting different Gßγ signaling interfaces.
