Regulation of protein phosphatase inhibitor-1 by cyclin-dependent kinase 5
Regulation of protein phosphatase inhibitor-1 by cyclin-dependent kinase 5
复制标题
DOI：
10.1074/jbc.m701046200
复制
发表时间：
2007-06-01
影响因子：
4.8
通讯作者：
Bibb, James A.
中科院分区：
文献类型：
--
作者：
Nguyen, Chan;Nishi, Akinori;Bibb, James A.
Inhibitor-1是蛋白磷酸酶1（PP-1）的第一个内源性抑制剂，以前报道它是细胞周期蛋白依赖性激酶5（Cdk 5）的底物（67）。进一步的研究揭示了通过质谱鉴定并通过定点诱变确认为Ser的额外Cdk 5位点的存在（6）。磷酸化丝氨酸（6）抑制剂-1的基础水平，通过针对该位点的磷酸化状态特异性抗体检测，存在于大脑的特定区域，并随年龄而变化。在纹状体中，Ser 6的基础体内磷酸化和去磷酸化分别由Cdk 5、PP-2A和PP-1介导。此外，钙调神经磷酸酶有助于在高钙条件下的去磷酸化。在生物化学测定中，Cdk 5依赖性的抑制剂-1在Ser（6）和Ser（67）处的磷酸化的功能被证明是抑制剂-1在Thr（35）处去磷酸化的能力的分子内损害;这种作用在体内的两个系统中重现。抑制剂-1在Thr（35）处的去磷酸化相当于蛋白质的失活，因为抑制剂-1仅在被cAMP依赖性激酶（PKA）在Thr（35）处磷酸化时充当PP-1的抑制剂。因此，抑制剂-1作为激酶和磷酸酶信号通路之间的关键连接点，将PP-1不仅与PKA和钙调磷酸酶而且与Cdk 5连接。
Inhibitor-1, the first identified endogenous inhibitor of protein phosphatase 1 ( PP-1), was previously reported to be a substrate for cyclin-dependent kinase 5 (Cdk5) at Ser(67). Further investigation has revealed the presence of an additional Cdk5 site identified by mass spectrometry and confirmed by site-directed mutagenesis as Ser(6). Basal levels of phospho-Ser(6) inhibitor-1, as detected by a phosphorylation state-specific antibody against the site, existed in specific regions of the brain and varied with age. In the striatum, basal in vivo phosphorylation and dephosphorylation of Ser6 were mediated by Cdk5, PP-2A, and PP-1, respectively. Additionally, calcineurin contributed to dephosphorylation under conditions of high Ca2+. In biochemical assays the function of Cdk5-dependent phosphorylation of inhibitor-1 at Ser(6) and Ser(67) was demonstrated to be an intramolecular impairment of the ability of inhibitor-1 to be dephosphorylated at Thr(35); this effect was recapitulated in two systems in vivo. Dephosphorylation of inhibitor-1 at Thr(35) is equivalent to inactivation of the protein, as inhibitor-1 only serves as an inhibitor of PP-1 when phosphorylated by cAMP-dependent kinase ( PKA) at Thr(35). Thus, inhibitor-1 serves as a critical junction between kinase-and phosphatase-signaling pathways, linking PP-1 to not only PKA and calcineurin but also Cdk5.