Protein phosphatase PP4 is overexpressed in human breast and lung tumors
Protein phosphatase PP4 is overexpressed in human breast and lung tumors
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蛋白磷酸酶 PP4 在人类乳腺和肺部肿瘤中过度表达
DOI：
10.1038/cr.2008.274
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发表时间：
2008-09
期刊：
影响因子：
--
通讯作者：
Zhao, Ailian
中科院分区：
文献类型：
--
作者：
Sun, Lingling;Zhong, Jianing;Wang, Haibo;Xu, Xingzhi;Yen, Yun;Zhong, Xueyan;Sang, Jianli;Pfeifer, Gerd P.;Chowdhury, Dipanjan;Xu, Yi;Li, Jing;Cai, Minhua;Wang, Bo;Liao, Ji;Zhao, Ailian
激酶和磷酸酶的可逆蛋白磷酸化是控制大多数（如果不是全部）细胞过程的最常见机制之一[1]。丝氨酸/苏氨酸残基的去磷酸化由两组不同的功能不同的丝氨酸/苏氨酸蛋白磷酸酶调节，PPM家族（其包括PP 2C）和PPP家族，其包括1型（PP 1）和2A型（PP 2A、PP 2B、PP 3、PP 4、PP 5、PP 6和PP 7）蛋白磷酸酶。2A型磷酸酶组的成员（PP 2A、PP 4和PP 6）在序列上最密切相关。它们对低剂量冈田酸（OA）或fostriecin的抑制敏感，这使它们与PP 1不同[1]。PP 2A的调节和功能已被深入研究。PP 2A由含有催化亚基（C）和支架亚基（A）的核心复合物组成，其与多种调节亚基和相互作用蛋白相互作用，将AC核心二聚体靶向特定底物和亚细胞位置[1]。许多不同类型的异源三聚体全酶的组装解释了PP 2A以及可能的PP 4和PP 6调节广泛的生物过程的能力。蛋白磷酸酶4催化亚基（PP 4C）在微管生长/组织化[2]、细胞凋亡[3，4]、肿瘤坏死因子信号传导[5]和前T细胞受体信号传导[4]中起重要作用。PP 4的消融导致小鼠胚胎死亡[4]。最近通过哺乳动物TAP标记技术和质谱法鉴定了人PP 4磷酸酶复合物PP 4C-PP 4 R2-PP 4 R3 [6]。在酿酒酵母中，pph 3（PP 4直向同源物）、psy 2（PP 4 R2直向同源物）和yb 1046 w（PP 4 R3直向同源物）突变体对顺铂治疗超敏，但pph 22（PP 2A直向同源物）突变体不敏感[6，7]。由于顺铂是一种复制依赖性DNA损伤剂[8]，这表明PP 4参与DNA损伤信号传导和/或修复。事实上，我们最近发现PP 4C使DNA复制过程中产生的γ-H2 AX去磷酸化[9]，而PP 2A使响应外源DNA损伤剂产生的γ-H2 AX去磷酸化[10]。为了进一步揭示蛋白磷酸酶PP 4的功能，与Bethyl Laboratories Inc.合作，我们针对PP 4C及其潜在的调节/结合蛋白（PP 4 R1、PP 4 R2、PP 4 R3 α和PP 4 R3 β）的每个靶点制备了四种抗肽多克隆抗体。我们鉴定了每种靶蛋白的至少一种抗体，其适用于免疫印迹和免疫沉淀，除了PP 4C抗体仅适用于免疫印迹（数据未显示）。免疫共沉淀试验（补充信息，数据S1）显示PP 4C形成三个互斥复合物乳腺癌细胞MDA-MB-231中的PP 4C-PP 4 R1、PP 4CPP 4 R2-PP 4 R3 α和PP 4C-PP 4 R2-PP 4 R3 β（补充资料，图S1）和MCF 7（数据未显示），其在暴露于DNA损伤剂如γ辐射、阿霉素或喜树碱（数据未显示）后没有改变。虽然PP 4 R3 α和PP 4 R3 β是近同源物，
Reversible protein phosphorylation by kinases and phosphatases is one of the most common mechanisms in controlling most, if not all, cellular processes [1]. Dephosphorylation of serine/threonine residues is regulated by two distinct groups of functionally diverse serine/threonine protein phosphatases, the PPM family (which includes PP2C) and the PPP family, which includes the type 1 (PP1) and the type 2A (PP2A, PP2B, PP3, PP4, PP5, PP6, and PP7) protein phosphatases. Members of the type 2A group of phosphatases (PP2A, PP4, and PP6) are the most closely related in sequence. They are sensitive to inhibition by low doses of okadaic acid (OA) or fostriecin, which distinguishes them from PP1 [1]. The regulation and function of PP2A have been thoroughly investigated. PP2A is composed of a core complex containing the catalytic subunit (C) and the scaffold subunit (A), which interacts with a wide variety of regulatory subunits and interacting proteins that target the AC core dimer to specific substrates and subcellular locations [1]. The assembly of many different types of heterotrimeric holoenzymes accounts for the ability of PP2A, and, possibly, PP4 and PP6, to regulate a wide range of biological processes. Protein phosphatases 4 catalytic subunit (PP4C) plays an important role in microtubule growth/organization [2], apoptosis [3, 4], tumor necrosis factor signaling [5], and pre-T-cell receptor signaling [4]. The ablation of PP4 leads to embryonic lethality in mice [4]. The human PP4 phosphatase complex, PP4C-PP4R2-PP4R3, was recently identified through mammalian TAP-tagging technique and mass spectrometry [6]. In Saccharomyces cerevisiae, the pph3 (PP4 orthologue), psy2 (PP4R2 orthologue), and yb1046w (PP4R3 orthologue) mutants, but not the pph22 (PP2A orthologue) mutant, are hypersensitive to cisplatin treatment [6, 7]. Since cisplatin is a replication-dependent DNA-damaging agent [8], this suggests that PP4 is involved in DNA damage signaling and/or repair. Indeed, we recently found that PP4C dephosphorylates γ-H2AX generated during DNA replication [9], while PP2A dephosphorylates γ-H2AX generated in response to exogenous DNA damaging agents [10].To further reveal the functions of protein phosphatase PP4, in collaboration with the Bethyl Laboratories Inc, we produced four anti-peptide polyclonal antibodies per target against PP4C and its potential regulatory/binding proteins (PP4R1, PP4R2, PP4R3α, and PP4R3β). We identified at least one antibody for each target protein, which was suitable for immunoblotting and immunoprecipitation, except that the PP4C antibody was only good for immunoblotting (data not shown). Co-immunoprecipitation assays (Supplementary information, Data S1) showed that PP4C formed three mutually exclusive complexes (PP4C-PP4R1, PP4CPP4R2-PP4R3α, and PP4C-PP4R2-PP4R3β) in the breast cancer cells MDA-MB-231 (Supplementary information, Figure S1) and MCF7 (data not shown), which were not altered after exposure to DNA-damaging agents such as γ radiation, adriamycin, or camptothecin (data not shown). Although PP4R3α and PP4R3β are close homologues,
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影响因子：
16
作者：
Chowdhury, Dipanjan;Xu, Xingzhi;Zhong, Xueyan;Ahmed, Fariyal;Zhong, Jianing;Liao, Ji;Dykxhoorn, Derek M.;Weinstock, David M.;Pfeifer, Gerd P.;Lieberman, Judy
通讯作者：
Lieberman, Judy
影响因子：
5.3
作者：
Shui, Jr-Wen;Hu, Mickey C. -T.;Tan, Tse-Hua
通讯作者：
Tan, Tse-Hua
影响因子：
7.8
作者：
Toyo-oka, Kazuhito;Mori, Daisuke;Yano, Yoshihisa;Shiota, Masayuki;Iwao, Hiroshi;Goto, Hidemasa;Inagaki, Masaki;Hiraiwa, Noriko;Muramatsu, Masami;Wynshaw-Boris, Anthony;Yoshiki, Atsushi;Hirotsune, Shinji
通讯作者：
Hirotsune, Shinji
影响因子：
--
作者：
R. Kühn;F. Schwenk
通讯作者：
R. Kühn;F. Schwenk
影响因子：
12.4
作者：
Mourtada-Maarabouni, M;Kirkham, L;Williams, GT
通讯作者：
Williams, GT