Phosphorylation of transcriptional coactivator peroxisome proliferator-activated receptor (PPAR)-binding protein (PBP) - Stimulation of transcriptional regulation by mitogen-activated protein kinase
Phosphorylation of transcriptional coactivator peroxisome proliferator-activated receptor (PPAR)-binding protein (PBP) - Stimulation of transcriptional regulation by mitogen-activated protein kinase
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DOI：
10.1074/jbc.m208829200
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发表时间：
2002-12-13
影响因子：
4.8
通讯作者：
Reddy, JK
中科院分区：
文献类型：
--
作者：
Misra, P;Owuor, ED;Reddy, JK
过氧化物酶体增殖物激活受体（Peroxisome proliferator-activated receptor，PPAR）结合蛋白（Peroxisome proliferator-activated receptor，PBP）是PPAR γ等转录因子的重要共激活因子。PBP是转录活性所需的多蛋白甲状腺激素受体相关蛋白（TRAP）/维生素D-3受体相互作用蛋白（DRIP）/激活剂募集辅因子（ARC）复合物的组成部分。为了研究PBP通过细胞信号通路的调节，我们鉴定了PBP的磷酸化位点。使用体外和体内方法的组合以及PBP磷酸化位点的诱变，我们鉴定了PBP上的六个磷酸化位点：丝氨酸656处的一个专有蛋白激酶A（PKA）磷酸化位点，丝氨酸796和丝氨酸1345处的两个蛋白激酶C（PKC）位点，丝氨酸756处的共同PKA/PKC位点，以及丝裂原活化蛋白激酶（MAPK）家族的两个细胞外信号调节激酶2位点，位于苏氨酸1017和苏氨酸1444。PBP与PPARgamma 1或9-顺式维甲酸（RXR）的维甲酸-X-受体的结合不依赖于它们的磷酸化状态，这意味着磷酸化修饰后蛋白质-蛋白质相互作用没有变化。RafBXB是MAPK信号转导通路的上游激活激酶，过表达RafBXB对PBP辅激活因子功能产生显著的加性诱导作用。这种作用被RafBXB的显性负突变体Raf-BXB 301的过表达显著减弱。这些结果将磷酸化鉴定为PBP的调节修饰事件，并证明Raf/MEK/MAPK级联的PBP磷酸化对PBP共激活因子功能产生积极影响。PKA和PKC磷酸化位点在PBP中的功能作用仍有待阐明。
Peroxisome proliferator-activated receptor (PPAR)binding protein (PBP) is an important coactivator for PPARgamma and other transcription factors. PBP is an integral component of a multiprotein thyroid hormone receptor-associated protein (TRAP)/vitamin D-3 receptor-interacting protein (DRIP)/activator-recruited cofactor (ARC) complex required for transcriptional activity. To study the regulation of PBP by cellular signaling pathways, we identified the phosphorylation sites of PBP. Using a combination of in vitro and in vivo approaches and mutagenesis of PBP phosphorylation sites, we identified six phosphorylation sites on PBP: one exclusive protein kinase A (PKA) phosphorylation site at serine 656, two protein kinase C (PKC) sites at serine 796 and serine 1345, a common PKA/PKC site at serine 756, and two extracellular signal-regulated kinase 2 sites of the mitogen-activated protein kinase (MAPK) family at threonine 1017 and threonine 1444. Binding of PBP to PPARgamma1 or retinoid-X-receptor for 9-cis-retinoic acid (RXR) is independent of their phosphorylation states, implying no changes in protein-protein interaction after modification by phosphorylation. Overexpression of RafBXB, an activated upstream kinase of the MAPK signal transduction pathway, exerts a significant additive inductive effect on PBP coactivator function. This effect is significantly diminished by overexpression of Raf-BXB301, a dominant negative mutant of RafBXB. These results identify phosphorylation as a regulatory modification event of PBP and demonstrate that PBP phosphorylation by Raf/MEK/MAPK cascade exerts a positive effect on PBP coactivator function. The functional role of PKA and PKC phosphorylation sites in PBP remains to be elucidated.