Drosophila phosphoinositide-dependent kinase-1 regulates apoptosis and growth via the phosphoinositide 3-kinase-dependent signaling pathway.

Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Taejon 305-701, Korea.
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.
Mesh Terms:
1-Phosphatidylinositol 3-Kinase, Animals, Apoptosis, Cell Division, Cyclic AMP-Dependent Protein Kinases, Drosophila, Drosophila Proteins, Protein-Serine-Threonine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-akt, Signal Transduction
Proc. Natl. Acad. Sci. U.S.A. May. 22, 2001; 98(11);6144-9 [PUBMED:11344272]
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