Protein kinase A activates protein phosphatase 2A by phosphorylation of the B56δ subunit
Protein kinase A activates protein phosphatase 2A by phosphorylation of the B56δ subunit
复制标题
DOI：
10.1073/pnas.0611532104
复制
发表时间：
2007-02-20
影响因子：
11.1
通讯作者：
Nairn, Angus C.
中科院分区：
文献类型：
--
作者：
Ahn, Jung-Hyuck;McAvoy, Thomas;Nairn, Angus C.
我们之前对纹状体切片中的 DARPP-32 的研究表明，D1 受体的激活导致 Thr-75（DARPP-32 中的 Cdk5 位点）的 cAMP 依赖性去磷酸化。在当前的研究中，我们阐明了蛋白磷酸酶 2A (PP2A) 被 cAMP/PKA 依赖性途径激活，导致 Thr-75 去磷酸化的机制。 PP2A 由与支架 A 亚基和多种 B 亚基结合的催化 C 亚基组成。我们发现 PP2A 的 A/C 亚基与 B56 delta（或 PPP2R5D）调节亚基相关，是一种活性 DARPP-32 磷酸酶。 HEK293 细胞中表达的 B56 δ 亚基形成异三聚体组装体，催化 DARPP-32（也共转染至 HEK293 细胞）中 Thr-75 处 PKA 介导的去磷酸化。 B56 δ 亚基被 PKA 磷酸化，这增加了 PP2A 在体外和体内的总体活性。在体外 B56 delta 中鉴定的四个 PKA 磷酸化位点中，发现 Ser-566 对于 PP2A 活性的调节至关重要。此外，纹状体切片中 D1 受体激活后，PKA 使 Ser-566 磷酸化。基于这些研究，我们提出 B56 delta/A/C PP2A 复合物调节 DARPP-32 Thr-75 的去磷酸化，从而帮助协调纹状体神经元中多巴胺能神经传递的功效。此外，通过这种机制刺激蛋白磷酸酶活性可能代表神经元和其他类型细胞中受 cAMP 调节的重要信号通路。
Our previous studies of DARPP-32 in striatal slices have shown that activation of D1 receptors leads to cAMP-dependent dephosphorylation of Thr-75, the Cdk5 site in DARPP-32. In the current study, we have elucidated a mechanism whereby protein phosphatase 2A (PP2A) is activated by a cAMP/PKA-dependent pathway, leading to dephosphorylation of Thr-75. PP2A consists of a catalytic C subunit that associates with the scaffolding A subunit and a variety of B subunits. We have found that the A/C subunits of PP2A, in association with the B56 delta (or PPP2R5D) regulatory subunit, is an active DARPP-32 phosphatase. The B56 delta subunit expressed in HEK293 cells forms a heterotrimeric assembly that catalyzes PKA-mediated dephosphorylation at Thr-75 in DARPP-32 (also cotransfected into HEK293 cells). The B56 delta subunit is phosphorylated by PKA, and this increases the overall activity of PP2A in vitro and in vivo. Among four PKA-phosphorylation sites identified in B56 delta in vitro, Ser-566 was found to be critical for the regulation of PP2A activity. Moreover, Ser-566 was phosphorylated by PKA in response to activation of D1 receptors in striatal slices. Based on these studies, we propose that the B56 delta/A/C PP2A complex regulates the dephosphorylation of DARPP-32 at Thr-75, thereby helping coordinate the efficacy of dopaminergic neurotransmission in striatal neurons. Moreover, stimulation of protein phosphatase activity by this mechanism may represent an important signaling pathway regulated by cAMP in neurons and other types of cell.