Apoptosis inhibitory activity of cytoplasmic p21Cip1/WAF1 in monocytic differentiation
Apoptosis inhibitory activity of cytoplasmic p21Cip1/WAF1 in monocytic differentiation
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DOI：
10.1093/emboj/18.5.1223
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发表时间：
1999-03-01
期刊：
影响因子：
11.4
通讯作者：
Mizutani, S
中科院分区：
文献类型：
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作者：
Asada, M;Yamada, T;Mizutani, S
p21（Cip 1/WAF 1）通过其N端和C端分别与G1环素/CDK复合物和增殖细胞核抗原（PCNA）结合来抑制细胞周期进程。p21（Cip 1/WAF 1）的细胞周期抑制活性与其核定位相关。在这里，我们报告了一种新的细胞质定位的p21（Cip 1/WAF 1）在外周血单核细胞（PBMs）和U937细胞进行单核细胞分化的体外治疗与维生素D3或异位表达的p21（Cip 1/WAF 1），并分析这种细胞质表达的生物学后果。U937细胞具有核内p21（Cip 1/WAF 1）表达，表现为G1期细胞周期阻滞，随后分化为单核细胞，后者与核内p21（Cip 1/WAF 1）的胞浆表达有关，同时伴随着对各种致瘤刺激的抵抗。生化分析表明，胞质p21（Cip 1/WAF 1）与凋亡信号调节激酶1（ASK 1）形成复合物，并抑制应激激活的MAP激酶级联反应。缺乏核定位信号（Delta NLS-p21）的p21的缺失突变体（Cip 1/WAF 1）的表达不诱导细胞周期停滞，也不诱导单核细胞分化，但通过结合和抑制应激激活的ASK 1活性而介导导致抗凋亡表型。因此，细胞质p21（Cip 1/WAF 1）本身充当细胞凋亡的抑制剂。我们的研究结果突出了p21（Cip 1/WAF 1）的不同功能作用，这是由其细胞内分布，并依赖于分化阶段。
p21(Cip1/WAF1) inhibits cell-cycle progression by binding to G(1) eydin/CDK complexes and proliferating cell nuclear antigen (PCNA) through its N- and C-terminal domains, respectively. The cell-cycle inhibitory activity of p21(Cip1/WAF1) is correlated with its nuclear localization. Here, we report a novel cytoplasmic localization of p21(Cip1/WAF1) in peripheral blood monocytes (PBMs) and in U937 cells undergoing monocytic differentiation by in vitro treatment with vitamin D3 or ectopic expression of p21(Cip1/WAF1), and analyze the biological consequences of this cytoplasmic expression. U937 cells which exhibit nuclear p21(Cip1/WAF1) demonstrated G1 cell-cycle arrest and subsequently differentiated into monocytes, The latter event was associated with a cytoplasmic expression of nuclear p21(Cip1/WAF1), concomitantly with a resistance to various apoptogenic stimuli. Biochemical analysis showed that cytoplasmic p21(Cip1/WAF1) forms a complex with the apoptosis signal-regulating kinase 1 (ASK1) and inhibits stress-activated MAP kinase cascade. Expression of a deletion mutant of p21(Cip1/WAF1) lacking the nuclear localization signal (Delta NLS-p21) did not induce cell cycle arrest nor monocytic differentiation, but led to an apoptosis-resistant phenotype, mediated by binding to and inhibition of the stress-activated ASK1 activity. Thus, cytoplasmic p21(Cip1/WAF1) it self acted as an inhibitor of apoptosis. Our findings highlight the different functional roles of p21(Cip1/WAF1), which are determined by its intracellular distribution and are dependent on the stage of differentiation.