title: 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.
abstract: The Akt protooncogene encodes a serine-threonine protein kinase which is activated by growth factor-generated signals that are transduced via the phosphatidylinositol 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 Sf9 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.
authors.affiliation: Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
authors.forename: K
authors.initials: K
authors.lastname: Datta
authors.forename: A
authors.initials: A
authors.lastname: Bellacosa
authors.forename: T O
authors.initials: TO
authors.lastname: Chan
authors.forename: P N
authors.initials: PN
authors.lastname: Tsichlis
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation; D006133:Growth Substances / Q000502:physiology*; D051379:Mice; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins; D015398:Signal Transduction; D018411:Spodoptera; D013329:Structure-Activity Relationship
chemical_list: D006133:Growth Substances; D015689:Oncogene Protein p21(ras); D015688:Oncogene Protein pp60(v-src); D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins