Gβγ interacts with mTOR and promotes its activation

Biochem Biophys Res Commun. 2014 Feb 7;444(2):218-23. doi: 10.1016/j.bbrc.2014.01.044. Epub 2014 Jan 22.

Abstract

Diverse G protein-coupled receptors depend on Gβγ 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 Gβγ. Thus, we tested the hypothesis that Gβγ directly contributes to mTOR signaling. Here, we demonstrate that endogenous mTOR interacts with Gβγ. Cell stimulation with serum modulates Gβγ interaction with mTOR. The carboxyl terminal region of mTOR, expressed as a GST-fusion protein, including the serine/threonine kinase domain, binds Gβγ heterodimers containing different Gβ subunits, except Gβ4. Both, mTORC1 and mTORC2 complexes interact with Gβ₁γ₂ 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 Gβγ and mTOR and the phosphorylation of AKT; whereas overexpression of Gαi interfered with the effect of Gβγ as promoter of p70S6K and AKT phosphorylation. Altogether, our results suggest that Gβγ positively regulates mTOR signaling via direct interactions and provide further support to emerging strategies based on the therapeutical potential of inhibiting different Gβγ signaling interfaces.

Keywords: AKT; Cell signaling; G-protein; G-protein coupled receptor; Gβγ; Raptor; Rictor; mTOR.

MeSH terms

  • Blotting, Western
  • Enzyme Activation / drug effects
  • GTP-Binding Protein beta Subunits / genetics
  • GTP-Binding Protein beta Subunits / metabolism*
  • GTP-Binding Protein gamma Subunits / genetics
  • GTP-Binding Protein gamma Subunits / metabolism*
  • HEK293 Cells
  • Humans
  • Immunoprecipitation
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Phosphorylation / drug effects
  • Protein Binding / drug effects
  • Proto-Oncogene Proteins c-akt / metabolism
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • Signal Transduction / drug effects
  • Sirolimus / pharmacology
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism*
  • Two-Hybrid System Techniques

Substances

  • GTP-Binding Protein beta Subunits
  • GTP-Binding Protein gamma Subunits
  • Multiprotein Complexes
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases, 70-kDa
  • Sirolimus