Alessi D R, Deak M, Casamayor A, Caudwell F B, Morrice N, Norman D G, Gaffney P, Reese C B, MacDougall C N, Harbison D, Ashworth A, Bownes M
Department of Biochemistry, University of Dundee, UK.
Curr Biol. 1997 Oct 1;7(10):776-89. doi: 10.1016/s0960-9822(06)00336-8.
The activation of protein kinase B (PKB, also known as c-Akt) is stimulated by insulin or growth factors and results from its phosphorylation at Thr308 and Ser473. We recently identified a protein kinase, termed PDK1, that phosphorylates PKB at Thr308 only in the presence of lipid vesicles containing phosphatidylinositol 3,4,5-trisphosphate (Ptdlns(3,4,5)P3) or phosphatidylinositol 3,4-bisphosphate (Ptdlns(3,4)P2).
We have cloned and sequenced human PDK1. The 556-residue monomeric enzyme comprises a catalytic domain that is most similar to the PKA, PKB and PKC subfamily of protein kinases and a carboxy-terminal pleckstrin homology (PH) domain. The PDK1 gene is located on human chromosome 16p13.3 and is expressed ubiquitously in human tissues. Human PDK1 is homologous to the Drosophila protein kinase DSTPK61, which has been implicated in the regulation of sex differentiation, oogenesis and spermatogenesis. Expressed PDK1 and DSTPK61 phosphorylated Thr308 of PKB alpha only in the presence of Ptdlns(3,4,5)P3 or Ptdlns(3,4)P2. Overexpression of PDK1 in 293 cells activated PKB alpha and potentiated the IGF1-induced phosphorylation of PKB alpha at Thr308. Experiments in which the PH domains of either PDK1 or PKB alpha were deleted indicated that the binding of Ptdlns(3,4,5)P3 or Ptdlns(3,4)P2 to PKB alpha is required for phosphorylation and activation by PDK1. IGF1 stimulation of 293 cells did not affect the activity or phosphorylation of PDK1.
PDK1 is likely to mediate the activation of PKB by insulin or growth factors. DSTPK61 is a Drosophila homologue of PDK1. The effect of Ptdlns(3,4,5)P3/Ptdlns(3,4)P2 in the activation of PKB alpha is at least partly substrate directed.
蛋白激酶B（PKB，也称为c - Akt）的激活受胰岛素或生长因子刺激，且源于其苏氨酸308（Thr308）和丝氨酸473（Ser473）位点的磷酸化。我们最近鉴定出一种蛋白激酶，称为PDK1，它仅在含有磷脂酰肌醇3,4,5 - 三磷酸（Ptdlns(3,4,5)P3）或磷脂酰肌醇3,4 - 二磷酸（Ptdlns(3,4)P2）的脂质囊泡存在时，才会使PKB在Thr308位点发生磷酸化。
我们克隆并测序了人类PDK1。这种由556个氨基酸残基组成的单体酶包含一个催化结构域，该结构域与蛋白激酶的PKA、PKB和PKC亚家族最为相似，以及一个羧基末端的普列克底物蛋白同源（PH）结构域。PDK1基因位于人类染色体16p13.3上，在人体组织中普遍表达。人类PDK1与果蝇蛋白激酶DSTPK61同源，后者参与性别分化、卵子发生和精子发生的调控。表达的PDK1和DSTPK61仅在Ptdlns(3,4,5)P3或Ptdlns(3,4)P2存在时，使PKBα的Thr308位点发生磷酸化。在293细胞中过表达PDK1可激活PKBα，并增强胰岛素样生长因子1（IGF1）诱导的PKBα在Thr308位点的磷酸化。缺失PDK1或PKBα的PH结构域的实验表明，Ptdlns(3,4,5)P3或Ptdlns(3,4)P2与PKBα的结合是PDK1进行磷酸化和激活所必需的。IGF1刺激293细胞并不影响PDK1的活性或磷酸化状态。
PDK1可能介导胰岛素或生长因子对PKB的激活。DSTPK61是PDK1的果蝇同源物。Ptdlns(3,4,5)P3/Ptdlns(3,4)P2在激活PKBα中的作用至少部分是针对底物的。
