Glycogen synthase kinase-3 beta is a dual specificity kinase differentially regulated by tyrosine and serine/threonine phosphorylation.
Glycogen synthase kinase-3 beta is a dual specificity kinase differentially regulated by tyrosine and serine/threonine phosphorylation.
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发表时间：
1994-05
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通讯作者：
Qiuling Wang;C. Fiol;A. DePaoli-Roach;P. Roach
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作者：
Qiuling Wang;C. Fiol;A. DePaoli-Roach;P. Roach
糖原合成酶激酶3 （GSK-3）参与控制几种代谢酶和转录因子对细胞外信号的响应。在过去，该酶被认为是一种蛋白质Ser/Thr激酶，尽管最近有报道称它含有Tyr(P) （Hughes， K., Nikolakaki， E., Plyte， S. E., Totty， N. F., and Woodgett， J. R. (1993) EMBO J. 12,803 -808）。克隆了兔骨骼肌GSK-3 β的cDNA，并在大肠杆菌中表达为活性蛋白激酶，表观分子量为M(r) 46,000，能够磷酸化几种已知的GSK-3底物。重组GSK-3 β在Ser， Thr和Tyr残基上进行自磷酸化，尽管通过抗Tyr(P)抗体判断该酶已经含有Tyr(P)。自磷酸化的最终结果是酶活性降低了3-5倍。从兔肌中纯化的GSK-3 α也发生了自磷酸化，但仅在丝氨酸和苏氨酸残基上。在这种情况下，与缺乏ATP/Mg2+的对照组相比，自磷酸化稳定了酶的活性。在所测试的几种磷酸酶中，lambda-噬菌体磷酸酶对丝氨酸和苏氨酸残基的去磷酸化最有效，但对酪氨酸残基没有去磷酸化作用。lambda-磷酸酶的作用导致GSK-3 β的再激活，约为初始活性的80%。蛋白酪氨酸磷酸酶PTP1B能够在Tyr残基上去磷酸化，导致酶活性降低。截断形式的GSK-3 β，表观M(r) 40,000，具有明显更高的比活性，在自磷酸化中存在缺陷，并且在自磷酸化反应中未失活。我们得出结论，GSK-3 β是一种双特异性蛋白激酶，与丝裂原活化蛋白激酶/ERK家族酶具有相同的意义。不同残基的磷酸化对酶活性的控制不同，丝氨酸/苏氨酸磷酸化导致失活，酪氨酸磷酸化导致活性增加。
The enzyme glycogen synthase kinase-3 (GSK-3) has been implicated in the control of several metabolic enzymes and transcription factors in response to extracellular signals. In the past, the enzyme has been considered to be a protein Ser/Thr kinase although it was recently reported to contain Tyr(P) (Hughes, K., Nikolakaki, E., Plyte, S. E., Totty, N. F., and Woodgett, J. R. (1993) EMBO J. 12, 803-808). A cDNA encoding rabbit skeletal muscle GSK-3 beta was cloned and expressed in Escherichia coli as an active protein kinase, with apparent M(r) 46,000, capable of phosphorylating several known GSK-3 substrates. Recombinant GSK-3 beta autophosphorylated on Ser, Thr, and Tyr residues although the enzyme already contained Tyr(P) as judged by its recognition by anti-Tyr(P) antibodies. The net result of the autophosphorylation was a 3-5-fold reduction in enzyme activity. GSK-3 alpha, purified from rabbit muscle, also underwent autophosphorylation but only on Ser and Thr residues. In this case, the autophosphorylation stabilized the enzyme activity compared with the control lacking ATP/Mg2+. Of several phosphatases tested, the lambda-phage phosphatase was the most effective in dephosphorylating at Ser and Thr residues but did not dephosphorylate at Tyr residues. The action of the lambda-phosphatase caused a reactivation of GSK-3 beta to approximately 80% of the starting activity. The protein tyrosine phosphatase PTP1B was able to dephosphorylate at Tyr residues leading to a reduction in enzyme activity. A truncated form of GSK-3 beta, apparent M(r) 40,000, had a significantly higher specific activity, was defective in autophosphorylation, and was not inactivated in the autophosphorylation reaction. We conclude that GSK-3 beta is a dual specificity protein kinase in the same sense as the mitogen-activated protein kinase/ERK family of enzymes. Phosphorylation at different residues differentially controls enzyme activity, Ser/Thr phosphorylation causing inactivation and Tyr phosphorylation resulting in increased activity.