Akt is a direct target of the phosphatidylinositol 3-kinase: Activation by growth factors, v-src and v-Ha-ras, in Sf9 and mammalian cells

Ketaki Datta, Alfonso Bellacosa, Tung O. Chan, Philip N. Tsichlis

Research output: Contribution to journalArticlepeer-review

261 Scopus citations

Abstract

The Akt protooncogene encodes a serine-threonine protein kinase which is activated by growth factor-generated signals that are transduced via the phosphatidyl-inositol 3'-kinase (PI3-K). Earlier studies suggested that the activation of Akt by PI3-K may be mediated by the binding of D3- phosphorylated phosphoinositides to the Akt pleckstrin homology (PH) domain. On the basis of these studies, it was hypothesized that Akt is a direct PI3- K target. To test this hypothesis, we reconstituted the pathway of Akt activation in baculovirus-infected Sf9 cells. The results showed that Akt, which is normally catalytically inactive in these cells, was activated when coexpressed with the activated PI3-K. Moreover, they showed that activated forms of c-Ha-ras (v-Ha-ras) and c-src (v-src or srcY527F), two molecules that transduce growth factor-generated signals, also activate Akt in a PI3- K-dependent manner in SP9 as well as NIH 3T3 cells. The activation of Akt by both growth factors and v-ras and v-src (or srcY527F) depends on the integrity of the Akt PH domain and carboxyl-terminal tail. These results show that Akt activation via the PI3-K can be faithfully reproduced in baculovirus-infected Sf9 cells. The same results support the hypothesis that Akt is a direct target of the PI3-K and identify cytoplasmic signaling molecules that may contribute to the transduction of PI3-K/Akt activation signals.

Original languageEnglish
Pages (from-to)30835-30839
Number of pages5
JournalJournal of Biological Chemistry
Volume271
Issue number48
DOIs
StatePublished - 1996

Keywords

  • 3T3 Cells
  • Animals
  • Cell Line
  • Enzyme Activation
  • Growth Substances/physiology
  • Mice
  • Oncogene Protein p21(ras)/metabolism
  • Oncogene Protein pp60(v-src)/metabolism
  • Phosphatidylinositol 3-Kinases
  • Phosphotransferases (Alcohol Group Acceptor)/metabolism
  • Protein Serine-Threonine Kinases/chemistry
  • Proto-Oncogene Proteins c-akt
  • Proto-Oncogene Proteins/chemistry
  • Recombinant Proteins
  • Signal Transduction
  • Spodoptera
  • Structure-Activity Relationship

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