TY - JOUR
T1 - Phosphorylation of the transcription factor forkhead family member FKHR by protein kinase B
AU - Rena, Graham
AU - Guo, Shaodong
AU - Cichy, Stephen C.
AU - Unterman, Terry G.
AU - Cohen, Philip
PY - 1999
Y1 - 1999
N2 - Protein kinase B lies "downstream" of phosphatidylinositide (PtdIns) 3-kinase and is thought to mediate many of the intracellular actions of insulin and other growth factors. Here we show that FKHR, a human homologue of the DAF16 transcription factor in Caenorhabditis elegans, is rapidly phosphorylated by human protein kinase B alpha (PKB alpha) at Thr-24, Ser-256, and Ser-319 in vitro and at a much faster rate than BAD, which is thought to be a physiological substrate for PKB, The same three sites, which all lie in the canonical PKB consensus sequences (Arg-Xaa-Arg-Xaa-Xaa-(Ser/Thr)), became phosphorylated when FKHR was cotransfected with either PKB or PDK1 (an upstream activator of PKB), All three residues became phosphorylated when 293 cells were stimulated with insulin-like growth factor 1 (IGF-1), The IGF-1-induced phosphorylation was abolished by the PtdIns 3-kinase inhibitor wortmannin but not by PD 98059 (an inhibitor of the mitogen-activated protein kinase cascade) or by rapamycin, These results indicate that FKHR is a physiological substrate of PKB and that it may mediate some of the physiological effects of PKB on gene expression. DAF16 is known to be a component of a signaling pathway that has been partially dissected genetically and includes homologues of the insulin/IGF-1 receptor, PtdIns 8-kinase and PKB, The conservation of Thr-24, Ser-256, and Ser-319 and the sequences surrounding them in DAF16 therefore suggests that DAF16 is also a direct substrate for PKB in C, elegans.
AB - Protein kinase B lies "downstream" of phosphatidylinositide (PtdIns) 3-kinase and is thought to mediate many of the intracellular actions of insulin and other growth factors. Here we show that FKHR, a human homologue of the DAF16 transcription factor in Caenorhabditis elegans, is rapidly phosphorylated by human protein kinase B alpha (PKB alpha) at Thr-24, Ser-256, and Ser-319 in vitro and at a much faster rate than BAD, which is thought to be a physiological substrate for PKB, The same three sites, which all lie in the canonical PKB consensus sequences (Arg-Xaa-Arg-Xaa-Xaa-(Ser/Thr)), became phosphorylated when FKHR was cotransfected with either PKB or PDK1 (an upstream activator of PKB), All three residues became phosphorylated when 293 cells were stimulated with insulin-like growth factor 1 (IGF-1), The IGF-1-induced phosphorylation was abolished by the PtdIns 3-kinase inhibitor wortmannin but not by PD 98059 (an inhibitor of the mitogen-activated protein kinase cascade) or by rapamycin, These results indicate that FKHR is a physiological substrate of PKB and that it may mediate some of the physiological effects of PKB on gene expression. DAF16 is known to be a component of a signaling pathway that has been partially dissected genetically and includes homologues of the insulin/IGF-1 receptor, PtdIns 8-kinase and PKB, The conservation of Thr-24, Ser-256, and Ser-319 and the sequences surrounding them in DAF16 therefore suggests that DAF16 is also a direct substrate for PKB in C, elegans.
U2 - 10.1074/jbc.274.24.17179
DO - 10.1074/jbc.274.24.17179
M3 - Article
SN - 0021-9258
VL - 274
SP - 17179
EP - 17183
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 24
ER -