Targeting of the transcription factor Max during apoptosis:: phosphorylation-regulated cleavage by caspase-5 at an unusual glutamic acid residue in position P1
Targeting of the transcription factor Max during apoptosis:: phosphorylation-regulated cleavage by caspase-5 at an unusual glutamic acid residue in position P1
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DOI：
10.1042/0264-6021:3580705
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发表时间：
2001-09-15
影响因子：
4.1
通讯作者：
Lüscher, B
中科院分区：
文献类型：
--
作者：
Krippner-Heidenreich, A;Talanian, RV;Lüscher, B
MAX是Myc/Max/Mad转录因子网络的中心组成部分，调控生长、分化和细胞凋亡。虽然Myc和Mad基因和蛋白受到高度调控，但Max的表达是结构性的，目前还不知道翻译后的调控。我们发现MAX在Fas诱导的细胞凋亡过程中是靶向的。MAX首先被去磷酸化，然后被半胱氨酸酶切割。在MAX中发现了两个caspase的特异性切割位点，一个位于IEVE(10)向下箭头，另一个位于SAFD(135)向下箭头G靠近C-末端，它们分别在体外被caspase-5和caspase-7切割。突变分析表明，这两个位点也在体内使用。因此，Max代表第一个caspase-5底物。谷氨酸残基后的异常切割只与全长的DNA结合的活性MAX蛋白一起观察到，而不与相应的多肽一起观察到，这表明结构决定因素可能对这种活性很重要。此外，蛋白激酶CK2介导的MAX在Ser-11处的磷酸化抑制了caspase-5的切割，Ser-11是体内先前定位的磷酸化位点。这些发现表明，caspase-5的切割需要Fas介导的MAX去磷酸化。MAX上发生的响应Fas信号的修饰会影响MAX/MAX同源二聚体的DNA结合活性。综上所述，我们的发现揭示了三个不同的过程，即caspase-5和caspase-7的去磷酸化和切割，这三个过程在Fas介导的细胞凋亡中针对Max，表明Myc/Max/Mad网络通过其中心成分来调节。
Max is the central component of the Myc/Max/Mad network of transcription factors that regulate growth, differentiation and apoptosis. Whereas the Myc and Mad genes and proteins are highly regulated, Max expression is constitutive and no posttranslational regulation is known. We have found that Max is targeted during Fas-induced apoptosis. Max is first dephosphorylated and subsequently cleaved by caspases. Two specific cleavage sites for caspases in Max were identified, one at IEVE(10)down arrowS and one at SAFD(135)down arrowG near the C-terminus, which are cleaved in vitro by caspase-5 and caspase-7 respectively. Mutational analysis indicates that both sites are also used in vivo. Thus Max represents the first caspase-5 substrate. The unusual cleavage after a glutamic acid residue is observed only with full-length, DNA-binding competent Max protein but not with corresponding peptides, suggesting that structural determinants might be important for this activity. Furthermore, cleavage by caspase-5 is inhibited by the protein kinase CK2-mediated phosphorylation of Max at Ser-11, a previously mapped phosphorylation site in vivo. These findings suggest that Fas-mediated dephosphorylation of Max is required for cleavage by caspase-5. The modifications that occur on Max in response to Fas signalling affect the DNA-binding activity of Max/Max homodimers. Taken together, our findings uncover three distinct processes, namely dephosphorylation and cleavage by caspase-5 and caspase-7, that target Max during Fas-mediated apoptosis, suggesting the regulation of the Myc/Max/Mad network through its central component.