KARATE: PKA-induced KRAS4B-RHOA-mTORC2 supercomplex phosphorylates AKT in insulin signaling and glucose homeostasis

Mol Cell. 2021 Nov 18;81(22):4622-4634.e8. doi: 10.1016/j.molcel.2021.09.001. Epub 2021 Sep 21.


AKT is a serine/threonine kinase that plays an important role in metabolism, cell growth, and cytoskeletal dynamics. AKT is activated by two kinases, PDK1 and mTORC2. Although the regulation of PDK1 is well understood, the mechanism that controls mTORC2 is unknown. Here, by investigating insulin receptor signaling in human cells and biochemical reconstitution, we found that insulin induces the activation of mTORC2 toward AKT by assembling a supercomplex with KRAS4B and RHOA GTPases, termed KARATE (KRAS4B-RHOA-mTORC2 Ensemble). Insulin-induced KARATE assembly is controlled via phosphorylation of GTP-bound KRAS4B at S181 and GDP-bound RHOA at S188 by protein kinase A. By developing a KARATE inhibitor, we demonstrate that KRAS4B-RHOA interaction drives KARATE formation. In adipocytes, KARATE controls insulin-dependent translocation of the glucose transporter GLUT4 to the plasma membrane for glucose uptake. Thus, our work reveals a fundamental mechanism that activates mTORC2 toward AKT in insulin-regulated glucose homeostasis.

Keywords: AKT; KRAS GTPase; PKA; RHOA GTPase; insulin; mTORC2.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3-L1 Cells
  • Adipocytes / cytology
  • Animals
  • Cell Membrane / metabolism
  • Cyclic AMP-Dependent Protein Kinases / chemistry*
  • Cytoskeleton / metabolism
  • Dictyostelium
  • Glucose / metabolism*
  • Glucose Transporter Type 4 / metabolism
  • Guanosine Diphosphate / chemistry
  • Guanosine Triphosphate / chemistry
  • HEK293 Cells
  • Humans
  • Insulin / metabolism*
  • Mechanistic Target of Rapamycin Complex 2 / chemistry*
  • Mice
  • Phosphorylation
  • Protein Transport
  • Proto-Oncogene Proteins c-akt / chemistry
  • Proto-Oncogene Proteins p21(ras) / chemistry
  • Proto-Oncogene Proteins p21(ras) / metabolism
  • rhoA GTP-Binding Protein / chemistry*


  • Glucose Transporter Type 4
  • Insulin
  • KRAS protein, human
  • KRAS4B protein, mouse
  • SLC2A4 protein, human
  • RHOA protein, human
  • Guanosine Diphosphate
  • Guanosine Triphosphate
  • AKT1 protein, human
  • Akt1 protein, mouse
  • Mechanistic Target of Rapamycin Complex 2
  • Proto-Oncogene Proteins c-akt
  • Cyclic AMP-Dependent Protein Kinases
  • Proto-Oncogene Proteins p21(ras)
  • RhoA protein, mouse
  • rhoA GTP-Binding Protein
  • Glucose