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Biochem Biophys Res Commun. 1998 May 8;246(1):76-81.

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

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Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.


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.

[Indexed for MEDLINE]

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