The role of 3-phosphoinositide-dependent protein kinase 1 in activating AGC kinases defined in embryonic stem cells
The role of 3-phosphoinositide-dependent protein kinase 1 in activating AGC kinases defined in embryonic stem cells
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DOI：
10.1016/s0960-9822(00)00441-3
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发表时间：
2000-04-20
期刊：
影响因子：
9.2
通讯作者：
Alessi, DR
中科院分区：
文献类型：
--
作者：
Williams, MR;Arthur, JSC;Alessi, DR
背景资料：蛋白激酶B（PKB）以及p70和p90核糖体S6激酶（分别为p70 S6激酶和p90 Rsk）通过两个残基的磷酸化而被激活，一个残基位于激酶结构域的“T环”中，另一个残基位于激酶结构域羧基末端的疏水基序中。3-磷酸肌醇依赖性蛋白激酶1（PDK 1）激活许多AGC激酶在体外通过磷酸化的T-环残基，但是否PDK 1也磷酸化的疏水基序，以及是否所有其他AGC激酶的底物PDK1.Results：小鼠胚胎干细胞（ES）中的PDK 1基因的两个副本被破坏是可行的。在PDK 2（-/-）ES细胞中，PKB、p70 S6激酶和p90 Rsk不被在PDK 1（+/+）细胞中诱导强活化的刺激物活化。其他AGC激酶-即蛋白激酶A（PKA），促分裂原和应激活化蛋白激酶1（MSK 1）和AMP活化蛋白激酶（AMPK）-在PDK 1（-/-）细胞中具有正常活性或被正常激活。胰岛素样生长因子1（IGF 1）在PDK 1（-/-）细胞中诱导PKB在其疏水基序磷酸化，而不是在其T环残基磷酸化。结论：PDK 1在体内可介导PKB、p70 S6激酶和p90 Rsk的激活，但对PKA、MSK 1和AMPK的激活无限速作用。另一种激酶在PDK 1（-/-）细胞中磷酸化PKB的疏水基序。PDK 1直接或通过激活另一种激酶磷酸化p70 S6激酶的疏水基序。
Background: Protein kinase B (PKB), and the p70 and p90 ribosomal S6 kinases (p70 S6 kinase and p90 Rsk, respectively), are activated by phosphorylation of two residues, one in the 'T-loop' of the kinase domain and, the other, in the hydrophobic motif carboxy terminal to the kinase domain. The 3-phosphoinositide-dependent protein kinase 1 (PDK1) activates many AGC kinases in vitro by phosphorylating the T-loop residue, but whether PDK1 also phosphorylates the hydrophobic motif and whether all other AGC kinases are substrates for PDK1 is unknown.Results: Mouse embryonic stem (ES) cells in which both copies of the PDK1 gene were disrupted were viable. In PDK2(-/-) ES cells, PKB, p70 S6 kinase and p90 Rsk were not activated by stimuli that induced strong activation in PDK1(+/+) cells. Other AGC kinases - namely, protein kinase A (PKA), the mitogen- and stress-activated protein kinase 1 (MSK1) and the AMP-activated protein kinase (AMPK) - had normal activity or were activated normally in PDK1(-/-) cells. The insulin-like growth factor 1 (IGF1) induced PKB phosphorylation at its hydrophobic motif, but not at its T-loop residue, in PDK1(-/-) cells. IGF1 did not induce phosphorylation of p70 S6 kinase at its hydrophobic motif in PDK1(-/-) cells.Conclusions: PDK1 mediates activation of PKB, p70 S6 kinase and p90 Rsk in vivo, but is not rate-limiting for activation of PKA, MSK1 and AMPK. Another kinase phosphorylates PKB at its hydrophobic motif in PDK1(-/-) cells. PDK1 phosphorylates the hydrophobic motif of p70 S6 kinase either directly or by activation of another kinase.