University of Liverpool, Cancer Research Centre, Liverpool L3 9TA, England, UK.
J Cell Biol. 2010 Dec 27;191(7):1315-32. doi: 10.1083/jcb.201008106.
Many protein kinases are activated by a conserved regulatory step involving T-loop phosphorylation. Although there is considerable focus on kinase activator proteins, the importance of specific T-loop phosphatases reversing kinase activation has been underappreciated. We find that the protein phosphatase 6 (PP6) holoenzyme is the major T-loop phosphatase for Aurora A, an essential mitotic kinase. Loss of PP6 function by depletion of catalytic or regulatory subunits interferes with spindle formation and chromosome alignment because of increased Aurora A activity. Aurora A T-loop phosphorylation and the stability of the Aurora A-TPX2 complex are increased in cells depleted of PP6 but not other phosphatases. Furthermore, purified PP6 acts as a T-loop phosphatase for Aurora A-TPX2 complexes in vitro, whereas catalytically inactive mutants cannot dephosphorylate Aurora A or rescue the PPP6C depletion phenotype. These results demonstrate a hitherto unappreciated role for PP6 as the T-loop phosphatase regulating Aurora A activity during spindle formation and suggest the general importance of this form of regulation.
许多蛋白激酶通过涉及 T 环磷酸化的保守调节步骤被激活。尽管人们对激酶激活蛋白的研究已经取得了很大进展，但对于特定的 T 环磷酸酶逆转激酶激活的重要性却一直被低估。我们发现蛋白磷酸酶 6（PP6）全酶是 Aurora A 的主要 T 环磷酸酶，Aurora A 是一种必不可少的有丝分裂激酶。由于 Aurora A 活性的增加，消耗催化或调节亚基会导致 PP6 功能丧失，从而干扰纺锤体的形成和染色体的排列。Aurora A 的 T 环磷酸化和 Aurora A-TPX2 复合物的稳定性在 PP6 耗尽的细胞中增加，但在其他磷酸酶耗尽的细胞中不会增加。此外，纯化的 PP6 在体外作为 Aurora A-TPX2 复合物的 T 环磷酸酶发挥作用，而无催化活性的突变体不能使 Aurora A 去磷酸化或挽救 PPP6C 耗尽表型。这些结果表明 PP6 在纺锤体形成过程中作为调节 Aurora A 活性的 T 环磷酸酶发挥了迄今为止尚未被认识到的作用，并提示了这种调节形式的普遍重要性。
