PI(3,4,5)P3Engagement Restricts Akt Activity to Cellular Membranes.
Protein kinase B/Akt regulates cellular metabolism, survival, and proliferation in response to hormones and growth factors. Hyperactivation of Akt is frequently observed in cancer, while Akt inactivation is associated with severe diabetes. Here, we investigated the molecular and cellular mechanisms that maintain Akt activity proportional to the activating stimulus. We show that binding of phosphatidylinositol-3,4,5-trisphosphate (PIP3) or PI(3,4)P2to the PH domain allosterically activates Akt by promoting high-affinity substrate binding. Conversely, dissociation from PIP3was rate limiting for Akt dephosphorylation, dependent on the presence of the PH domain. In cells, active Akt associated primarily with cellular membranes. In contrast, a transforming mutation that uncouples kinase activation from PIP3resulted in the accumulation of hyperphosphorylated, active Akt in the cytosol. Our results suggest that intramolecular allosteric and cellular mechanisms cooperate to restrict Akt activity to cellular membranes, thereby enhancing the fidelity of Akt signaling and the specificity of downstream substrate phosphorylation.
Department of Structural and Computational Biology, Max F. Perutz Laboratories, Vienna Biocenter (VBC), Campus Vienna Biocenter 5, 1030 Vienna, Austria.
Michael
M
Ebner
Department of Structural and Computational Biology, Max F. Perutz Laboratories, Vienna Biocenter (VBC), Campus Vienna Biocenter 5, 1030 Vienna, Austria.
Iva
I
Lučić
Department of Structural and Computational Biology, Max F. Perutz Laboratories, Vienna Biocenter (VBC), Campus Vienna Biocenter 5, 1030 Vienna, Austria; Department of Medical Biochemistry, Medical University of Vienna, Vienna Biocenter (VBC), Dr. Bohr-Gasse 9, 1030 Vienna, Austria. Electronic address: thomas.leonard@mfpl.ac.at.
Thomas A
TA
Leonard
Department of Structural and Computational Biology, Max F. Perutz Laboratories, Vienna Biocenter (VBC), Campus Vienna Biocenter 5, 1030 Vienna, Austria; Department of Medical Biochemistry, Medical University of Vienna, Vienna Biocenter (VBC), Dr. Bohr-Gasse 9, 1030 Vienna, Austria. Electronic address: ivan.yudushkin@mfpl.ac.at.
Ivan
I
Yudushkin
D000494:Allosteric Regulation; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D061986:MCF-7 Cells; D009154:Mutation; D010716:Phosphatidylinositols / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D051057:Proto-Oncogene Proteins c-akt / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
D010716:Phosphatidylinositols; C118303:phosphoinositide-3,4,5-triphosphate; C118301:phosphoinositide-3,4-bisphosphate; D051057:Proto-Oncogene Proteins c-akt
AGC kinases; allostery; cellular membranes; cellular signaling; fluorescence correlation spectroscopy; fluorescence cross-correlation spectroscopy; phosphatidylinositol-3,4,5-trisphosphate; protein kinase B/Akt; protein phosphatases; signal transduction