Polyoma middle T antigen activates the Ser/Thr kinase Akt in a PI3-kinase-dependent manner

Biochem Biophys Res Commun. 1998 May 8;246(1):76-81. doi: 10.1006/bbrc.1998.8575.


Polyoma middle T antigen (PMT) was originally identified as the tumorigenic component of the polyomavirus genome. To investigate whether the serine/ threonine kinase Akt/PKB, which is the proto-oncogene transduced by the transforming AKT8 retrovirus, is activated by PMT, 3T3-L1 fibroblasts were stably transfected with wild type PMT. PMT expression accelerated glucose transport and increased phosphorylation of p70 S6-kinase and MAPK. PMT expression also stimulated Akt kinase activity 7 fold as compared to untreated, mock infected cells. This stimulation rivaled that obtained following insulin treatment of both mock and PMT infected cells. Akt activation and phosphorylation were eliminated in a PMT mutant incapable of interacting with PI3-kinase, but not one which does not interact with Shc, and correlated closely to the amount of PI3-kinase activity in anti-phosphotyrosine immunoprecipitates. These results indicate that the PI3-kinase pathway is requisite, but the Shc pathway is dispensable, for Akt activation. The studies further suggest that Akt may participate in PMT and PI3-kinase's regulation of cellular transformation and tumorigenesis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Animals
  • Antigens, Polyomavirus Transforming / genetics
  • Antigens, Polyomavirus Transforming / metabolism*
  • Cell Transformation, Neoplastic
  • Enzyme Activation
  • Mice
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Polyomavirus / genetics
  • Polyomavirus / immunology
  • Polyomavirus / pathogenicity
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Transfection


  • Antigens, Polyomavirus Transforming
  • Proto-Oncogene Proteins
  • Phosphatidylinositol 3-Kinases
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt