Abundant expression of Dec1/stra13/sharp2 in colon carcinoma: its antagonizing role in serum deprivation-induced apoptosis and selective inhibition of procaspase activation
Abundant expression of Dec1/stra13/sharp2 in colon carcinoma: its antagonizing role in serum deprivation-induced apoptosis and selective inhibition of procaspase activation
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DOI：
10.1042/bj20020514
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发表时间：
2002-10-15
影响因子：
4.1
通讯作者：
Yan, BF
中科院分区：
文献类型：
--
作者：
Li, YX;Zhang, H;Yan, BF
碱性螺旋-环-螺旋（bHLH）蛋白与发育事件如细胞分化和谱系定型密切相关。bHLH基序中的HLH结构域负责二聚化，而碱性区域介导DNA结合。基于序列比对和结构域分析，差异表达的软骨细胞/刺激与视黄酸/分裂和毛相关蛋白（DEC/STRA/SHARPs）代表一类新的bHLH蛋白。本研究描述了DEC 1的功能特性。差减实验和印迹分析表明，DEC 1在结肠癌中高表达，而在癌旁正常组织中不表达。几种细胞周期阻滞剂显著诱导DEC 1表达。稳定的转染与四环素诱导的结构表明，DEC 1引起增殖抑制，拮抗血清剥夺诱导的细胞凋亡，并选择性地抑制前半胱氨酸天冬氨酸蛋白酶的激活。这些活性与四环素诱导的DEC 1的丰度高度相关。表达突变DEC 1（缺乏DNA结合域）的稳定转染子既不表现出增殖抑制作用，也不表现出凋亡拮抗作用，这表明DNA结合是这些作用所必需的。酶法和免疫印迹分析表明，四环素诱导的DEC 1显着降低了半胱氨酸蛋白酶原3，7和9的激活，但不半胱氨酸蛋白酶原8。相对于半胱天冬酶原8，对半胱天冬酶原3、7和9的活化的选择性抑制表明DEC 1介导的抗凋亡是通过阻断经由线粒体启动的凋亡途径来实现的。结果在功能上将DEC 1与其他bHLH蛋白区分开来，并将该因子与肿瘤发生直接联系起来。
The basic helix-loop-helix (bHLH) proteins are intimately associated with developmental events such as cell differentiation and lineage commitment. The HLH domain in the bHLH motif is responsible for dimerization, whereas the basic region mediates DNA binding. Based on sequence alignment and domain analysis, differentially expressed in chondrocytes/stimulated with retinoic acid/split and hairy-related proteins (DEC/STRA/SHARPs) represent a new class of bHLH proteins. The present study describes the functional characterization of DEC1. Subtractive experiments and blotting analyses demonstrated that DEC1 was highly expressed in colon carcinomas, but not in the adjacent normal tissues. Several cell cycle blockers markedly induced DEC1 expression. Stable transfectants with a tetracycline-inducible construct demonstrated that DEC1 caused proliferation inhibition, antagonized serum deprivation-induced apoptosis and selectively inhibited the activation of procaspases. These activities were highly correlated with the abundance of tetracycline-induced DEC1. Stable transfectants expressing a mutant DEC1 (lacking the DNA-binding domain) exhibited neither proliferation inhibition nor apoptotic antagonism, which suggests that DNA binding is required for these actions. Enzymic assays and immunoblotting analyses demonstrated that induction of DEC1 by tetracycline significantly decreased the activation of procaspases 3, 7 and 9 but not procaspase 8. The selective suppression on the activation of procaspases 3, 7 and 9 over procaspase 8 suggests that DEC1-mediated anti-apoptosis is achieved by blocking apoptotic pathways initiated via the mitochondria. The results functionally distinguish DEC1 from other bHLH proteins and directly link this factor to oncogenesis.