Lizcano Jose M, Göransson Olga, Toth Rachel, Deak Maria, Morrice Nick A, Boudeau Jérôme, Hawley Simon A, Udd Lina, Mäkelä Tomi P, Hardie D Grahame, Alessi Dario R
MRC Protein Phosphorylation Unit, School of Life Sciences, University of Dundee, Dundee, UK.
EMBO J. 2004 Feb 25;23(4):833-43. doi: 10.1038/sj.emboj.7600110. Epub 2004 Feb 19.
We recently demonstrated that the LKB1 tumour suppressor kinase, in complex with the pseudokinase STRAD and the scaffolding protein MO25, phosphorylates and activates AMP-activated protein kinase (AMPK). A total of 12 human kinases (NUAK1, NUAK2, BRSK1, BRSK2, QIK, QSK, SIK, MARK1, MARK2, MARK3, MARK4 and MELK) are related to AMPK. Here we demonstrate that LKB1 can phosphorylate the T-loop of all the members of this subfamily, apart from MELK, increasing their activity >50-fold. LKB1 catalytic activity and the presence of MO25 and STRAD are required for activation. Mutation of the T-loop Thr phosphorylated by LKB1 to Ala prevented activation, while mutation to glutamate produced active forms of many of the AMPK-related kinases. Activities of endogenous NUAK2, QIK, QSK, SIK, MARK1, MARK2/3 and MARK4 were markedly reduced in LKB1-deficient cells. Neither LKB1 activity nor that of AMPK-related kinases was stimulated by phenformin or AICAR, which activate AMPK. Our results show that LKB1 functions as a master upstream protein kinase, regulating AMPK-related kinases as well as AMPK. Between them, these kinases may mediate the physiological effects of LKB1, including its tumour suppressor function.
我们最近证明，肿瘤抑制激酶LKB1与假激酶STRAD和支架蛋白MO25形成复合物，可磷酸化并激活AMP激活的蛋白激酶（AMPK）。共有12种人类激酶（NUAK1、NUAK2、BRSK1、BRSK2、QIK、QSK、SIK、MARK1、MARK2、MARK3、MARK4和MELK）与AMPK相关。在此我们证明，除MELK外，LKB1可磷酸化该亚家族所有成员的T环，使其活性增加50倍以上。LKB1的催化活性以及MO25和STRAD的存在是激活所必需的。将LKB1磷酸化的T环苏氨酸突变为丙氨酸可阻止激活，而突变为谷氨酸则产生许多AMPK相关激酶的活性形式。在LKB1缺陷细胞中，内源性NUAK2、QIK、QSK、SIK、MARK1、MARK2/3和MARK4的活性明显降低。二甲双胍或AICAR可激活AMPK，但它们均不能刺激LKB1或AMPK相关激酶的活性。我们的结果表明，LKB1作为主要的上游蛋白激酶，可调节AMPK相关激酶以及AMPK。这些激酶之间可能介导LKB1的生理效应，包括其肿瘤抑制功能。
