Akt Protein Kinase Inhibits Rac1-GTP Binding through Phosphorylation at Serine 71 of Rac1

A putative Akt kinase phosphorylation site ( 64 yd R I R plSYp 73 ) was found in Rac1/CDC42 and Rho family proteins (RhoA, RhoB, RhoC, and RhoG). Phosphorylation of Rac1 by Akt kinase was assayed with recombinant Rac1 protein and the fluorescein-labeled Rac1 peptide. It was shown that the Rac1 pepti...

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Bibliographic Details
Published in:The Journal of biological chemistry 2000-01, Vol.275 (1), p.423-428
Main Authors: Kwon, T, Kwon, D Y, Chun, J, Kim, J H, Kang, S S
Format: Article
Language:English
Subjects:
Androstadienes - pharmacology
Chromones - pharmacology
Guanosine Triphosphate - metabolism
Mitogen-Activated Protein Kinases
Morpholines - pharmacology
Oligopeptides - metabolism
Peptide Fragments - metabolism
Phosphatidylinositol 3-Kinases - metabolism
Phosphorylation
Protein Kinases - metabolism
Protein-Serine-Threonine Kinases
Proto-Oncogene Proteins - metabolism
Proto-Oncogene Proteins c-akt
rac1 GTP-Binding Protein - metabolism
Signal Transduction
Wortmannin
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Summary:A putative Akt kinase phosphorylation site ( 64 yd R I R plSYp 73 ) was found in Rac1/CDC42 and Rho family proteins (RhoA, RhoB, RhoC, and RhoG). Phosphorylation of Rac1 by Akt kinase was assayed with recombinant Rac1 protein and the fluorescein-labeled Rac1 peptide. It was shown that the Rac1 peptide and the recombinant protein were phosphorylated by the activated recombinant Akt kinase and the lysate of SK-MEL28 cells, a human melanoma cell line. The phosphorylation of Rac1 inhibited its GTP-binding activity without any significant change in GTPase activity. Both the GTP-binding and GTPase activities of Rac1 S71A protein (with the serine residue to be phosphorylated replaced with alanine) were abolished regardless of the treatment of Akt kinase. Akt kinase activity and Rac1 peptide phosphorylation were down-regulated by the treatment of SK-MEL28 cells with wortmannin or LY294002 (a phosphoinositide 3-kinase inhibitor), but JNK/SAPK kinase activity was up-regulated. Thus, the results suggest that Akt kinase of the phosphoinositide 3-kinase signal transduction pathway phosphorylates serine 71 of Rac1 as one of its authentic substrates and modulates the Rac1 signal transduction pathway through phosphorylation.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.275.1.423