title: Drosophila phosphoinositide-dependent kinase-1 regulates apoptosis and growth via the phosphoinositide 3-kinase-dependent signaling pathway.
abstract: Phosphoinositide-dependent kinase-1 (PDK-1) is a central mediator of the cell signaling between phosphoinositide 3-kinase (PI3K) and various intracellular serine/threonine kinases including Akt/protein kinase B (PKB), p70 S6 kinases, and protein kinase C. Recent studies with cell transfection experiments have implied that PDK-1 may be involved in various cell functions including cell growth and apoptosis. However, despite its pivotal role in cellular signalings, the in vivo functions of PDK-1 in a multicellular system have rarely been investigated. Here, we have isolated Drosophila PDK-1 (dPDK-1) mutants and characterized the in vivo roles of the kinase. Drosophila deficient in the dPDK-1 gene exhibited lethality and an apoptotic phenotype in the embryonic stage. Conversely, overexpression of dPDK-1 increased cell and organ size in a Drosophila PI3K-dependent manner. dPDK-1 not only could activate Drosophila Akt/PKB (Dakt1), but also substitute the in vivo functions of its mammalian ortholog to activate Akt/PKB. This functional interaction between dPDK-1 and Dakt1 was further confirmed through genetic analyses in Drosophila. On the other hand, cAMP-dependent protein kinase, which has been proposed as a possible target of dPDK-1, did not interact with dPDK-1. In conclusion, our findings provide direct evidence that dPDK-1 regulates cell growth and apoptosis during Drosophila development via the PI3K-dependent signaling pathway and demonstrate our Drosophila system to be a powerful tool for elucidating the in vivo functions and targets of PDK-1.
authors.affiliation: Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Taejon 305-701, Korea.
authors.forename: K S
authors.initials: KS
authors.lastname: Cho
authors.forename: J H
authors.initials: JH
authors.lastname: Lee
authors.forename: S
authors.initials: S
authors.lastname: Kim
authors.forename: D
authors.initials: D
authors.lastname: Kim
authors.forename: H
authors.initials: H
authors.lastname: Koh
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.forename: C
authors.initials: C
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Chung
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000818:Animals; D017209:Apoptosis; D002455:Cell Division; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004330:Drosophila / Q000196:embryology; D029721:Drosophila Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction
chemical_list: D064413:3-Phosphoinositide-Dependent Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D029721:Drosophila Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C494917:Akt1 protein, Drosophila; C578560:Pdk1 protein, Drosophila