Insulin stimulates the kinase activity of RAC-PK, a pleckstrin homology domain containing ser/thr kinase

EMBO J. 1995 Sep 1;14(17):4288-95.


In the present study, insulin is shown to rapidly stimulate by 8- to 12-fold the enzymatic activity of RAC-PK alpha, a pleckstrin homology domain containing ser/thr kinase. In contrast, activation of protein kinase C by phorbol esters had almost no effect on the enzymatic activity of RAC-PK alpha. Insulin activation was accompanied by a shift in molecular weight of the RAC-PK alpha protein, and the activated kinase was deactivated by treatment with a phosphatase, indicating that insulin activated the enzyme by stimulating its phosphorylation. This insulin-induced shift in RAC-PK was also observed in primary rat epididymal adipocytes, as well as in a muscle cell line called C2C12 cells. The insulin-stimulated increase in RAC-PK alpha activity was inhibited by wortmannin (an inhibitor of phosphatidylinositol 3-kinase) in a dose-dependent manner with a half-maximal inhibition of 10 nM, but not by 20 ng/ml of rapamycin. Activation of RAC-PK alpha activity was also observed in a variant RAC lacking the pleckstrin homology domain. These results indicate that RAC-PK alpha activity can be regulated by the insulin receptor. RAC-PK alpha may therefore play a general role in intracellular signaling mediated by receptor tyrosine kinases.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • Blood Proteins / chemistry*
  • CHO Cells
  • Cloning, Molecular
  • Cricetinae
  • DNA Primers
  • Enzyme Activation
  • Epitopes / analysis
  • HeLa Cells
  • Hemagglutinins
  • Humans
  • Insulin / pharmacology*
  • Kinetics
  • Molecular Sequence Data
  • Phosphatidylinositol 3-Kinases
  • Phosphoproteins*
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism
  • Polymerase Chain Reaction
  • Protein-Serine-Threonine Kinases / biosynthesis
  • Protein-Serine-Threonine Kinases / chemistry*
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Signal Transduction
  • Transfection


  • Blood Proteins
  • DNA Primers
  • Epitopes
  • Hemagglutinins
  • Insulin
  • Phosphoproteins
  • Recombinant Proteins
  • platelet protein P47
  • Phosphatidylinositol 3-Kinases
  • Phosphotransferases (Alcohol Group Acceptor)
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt