Autoregulation of the mechanistic target of rapamycin (mTOR) complex 2 integrity is controlled by an ATP-dependent mechanism.
Nutrients are essential for living organisms because they fuel biological processes in cells. Cells monitor nutrient abundance and coordinate a ratio of anabolic and catabolic reactions. Mechanistic target of rapamycin (mTOR) signaling is the essential nutrient-sensing pathway that controls anabolic processes in cells. The central component of this pathway is mTOR, a highly conserved and essential protein kinase that exists in two distinct functional complexes. The nutrient-sensitive mTOR complex 1 (mTORC1) controls cell growth and cell size by phosphorylation of the regulators of protein synthesis S6K1 and 4EBP1, whereas its second complex, mTORC2, regulates cell proliferation by functioning as the regulatory kinase of Akt and other members of the AGC kinase family. The regulation of mTORC2 remains poorly characterized. Our study shows that the cellular ATP balance controls a basal kinase activity of mTORC2 that maintains the integrity of mTORC2 and phosphorylation of Akt on the turn motif Thr-450 site. We found that mTOR stabilizes SIN1 by phosphorylation of its hydrophobic and conserved Ser-260 site to maintain the integrity of mTORC2. The optimal kinase activity of mTORC2 requires a concentration of ATP above 1.2 mM and makes this kinase complex highly sensitive to ATP depletion. We found that not amino acid but glucose deprivation of cells or acute ATP depletion prevented the mTOR-dependent phosphorylation of SIN1 on Ser-260 and Akt on Thr-450. In a low glucose medium, the cells carrying a substitution of SIN1 with its phosphomimetic mutant show an increased rate of cell proliferation related to a higher abundance of mTORC2 and phosphorylation of Akt. Thus, the homeostatic ATP sensor mTOR controls the integrity of mTORC2 and phosphorylation of Akt on the turn motif site.
Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77030.
Chien-Hung
CH
Chen
Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan.
Vladimir
V
Kiyan
Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan.
Assylbek A
AA
Zhylkibayev
Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan.
Dubek
D
Kazyken
Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan.
Olga
O
Bulgakova
Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Department of Biomedical Engineering, University of Houston, Houston, Texas 77004.
Kent E
KE
Page
Department of Natural Sciences, L. N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan.
Rakhmet I
RI
Bersimbaev
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142.
Eric
E
Spooner
Department of Molecular and Cellular Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77030. Electronic address: dsarbass@mdanderson.org.
Dos D
DD
Sarbassov
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs; D049109:Cell Proliferation; D006367:HeLa Cells; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C493277:MAPKAP1 protein, human; D046912:Multiprotein Complexes; D000255:Adenosine Triphosphate; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases
ATP; Glucose; Protein Phosphorylation; mTOR; mTOR Complex (mTORC)