Disruption of Serine/Threonine Protein Phosphatase 5 (PP5: PPP5c) in Mice Reveals a Novel Role for PP5 in the Regulation of Ultraviolet Light-induced Phosphorylation of SerinefThreonine Protein Kinase Chk1 (CHEK1)
Disruption of Serine/Threonine Protein Phosphatase 5 (PP5: PPP5c) in Mice Reveals a Novel Role for PP5 in the Regulation of Ultraviolet Light-induced Phosphorylation of SerinefThreonine Protein Kinase Chk1 (CHEK1)
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DOI：
10.1074/jbc.m111.244053
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发表时间：
2011-11-25
影响因子：
4.8
通讯作者：
Honkanen, Richard E.
中科院分区：
文献类型：
--
作者：
Amable, Lauren;Grankvist, Nina;Honkanen, Richard E.
PPS是一种广泛表达的Ser/Thr蛋白磷酸酶。已在人类癌症中观察到高水平的PP 5，并且组成型PP 5过表达有助于肿瘤发展的小鼠模型中的肿瘤进展。然而，PP 5在物种间高度保守，其在正常组织中的作用尚不清楚。在此，为了帮助评估PP 5的生物学作用，产生了CrelloxP条件小鼠系。与其他PPP家族磷酸酶（例如PP 2A和PP 4）的遗传破坏相关的早期胚胎致死率形成鲜明对比，与在发育早期开始普遍表达Cre重组酶的小鼠品系（例如MeuCre 40和ACTB-Cre）杂交产生了可行且可生育的PP 5缺陷小鼠。PP 5完全破坏引起的表型差异很小，这表明PP 5的小分子抑制剂不会具有广泛的全身毒性。对PP 5在从PP 5缺陷胚胎（PP 5 '小鼠胚胎成纤维细胞）产生的成纤维细胞中的作用的检查证实了PP 5的一些已知作用，并鉴定了PP 5的新作用。PP 5（-/-）小鼠胚胎成纤维细胞表现出对UV光、羟基脲和喜树碱的敏感性增加，这些物质是ATR（共济失调-毛细血管扩张和Rad 3相关）激酶的已知激活剂。进一步的研究揭示了一个以前未被认识到的作用，为PP 5下游的ATR激活的UV光诱导的反应。PP 5的遗传破坏与Chk 1上单个老年人（Ser-345）的磷酸化增强和延长、p53肿瘤抑制蛋白（p53）丝氨酸18位磷酸化增加和p53蛋白水平增加有关。在人类细胞中也观察到PP 5在Chk 1磷酸化调节中的类似作用。
PPS is a ubiquitously expressed Ser/Thr protein phosphatase. High levels of PP5 have been observed in human cancers, and constitutive PP5 overexpression aids tumor progression in mouse models of tumor development. However, PP5 is highly conserved among species, and the roles of PP5 in normal tissues are not clear. Here, to help evaluate the biological actions of PP5, a CrelloxP-conditional mouse line was generated. In marked contrast to the early embryonic lethality associated with the genetic disruption of other PPP family phosphatases (e.g. PP2A and PP4), intercrosses with mouse lines that ubiquitously express Cre recombinase starting early in development (e.g. MeuCre40 and ACTB-Cre) produced viable and fertile PP5-deficient mice. Phenotypic differences caused by the total disruption of PP5 were minor, suggesting that small molecule inhibitors of PP5 will not have widespread systemic toxicity. Examination of roles for PP5 in fibroblasts generated from PP5, deficient embryos (PP5' mouse embryonic fibroblasts) confirmed some known roles and identified new actions for PP5. PP5(-/-) mouse embryonic fibroblasts demonstrated increased sensitivity to UV light, hydroxyurea, and camptothecin, which are known activators of ATR (ataxia-telangiectasia and Rad3-related) kinase. Further study revealed a previously unrecognized role for PP5 downstream of ATR activation in a UV light-induced response. The genetic disruption of PP5 is associated with enhanced and prolonged phosphorylation of a single senile (Ser-345) on Chk1, increased phosphorylation of the p53 tumor suppressor protein (p53) at serine 18, and increased p53 protein levels. A comparable role for PP5 in the regulation of Chk1 phosphorylation was also observed in human cells.