SCF(beta-TrCP1) controls Smad4 protein stability in pancreatic cancer cells.
SCF(beta-TrCP1) controls Smad4 protein stability in pancreatic cancer cells.
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发表时间：
2005
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通讯作者：
M. Wan;Jin Huang;N. Jhala;E. Tytler;Lei Yang;S. Vickers;Yi Tang;Chongyuan Lu;Ning Wang
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作者：
M. Wan;Jin Huang;N. Jhala;E. Tytler;Lei Yang;S. Vickers;Yi Tang;Chongyuan Lu;Ning Wang
Smad4，也被称为胰腺癌基因座4 （DPC4）缺失，是转化生长因子(TGF)- β相关配体激活的信号转导通路中的关键辅助因子，调节细胞生长和分化。Smad4/DPC4突变已在大约50%的胰腺腺癌中被发现。在这里，我们报道了SCF(β - trcp1)，一种泛素（E3）连接酶，是胰腺癌细胞中Smad4蛋白降解的关键决定因素。我们发现该E3连接酶中的F-box蛋白β - trcp1与Smad4相互作用，并且SCF（β - trcp1）通过降低Smad4的稳定性来抑制tgf - β在胰腺癌细胞中的生物活性。免疫组化法观察到人胰腺导管腺癌细胞中Smad4蛋白水平极低。通过分析胰腺肿瘤衍生的Smad4突变体，我们发现大多数点突变的Smad4蛋白，除了在突变簇区域内或非常靠近突变簇区域外，与β - trcp1表现出更高的相互作用亲和力，并且SCF（β - trcp1）显著提高了蛋白泛素化。此外，由于SCF（β - trcp1）的作用，两种携带Smad4点突变的癌细胞系AsPC-1和Caco-2表现出Smad4蛋白的快速降解。在胰腺癌细胞中，逆转录病毒递送的β - trcp1 siRNA升高了Smad4水平和tgf - β信号。因此，抑制smad4特异性E3连接酶可能是胰腺癌治疗干预的靶点。
Smad4, also known as deleted in pancreatic carcinoma locus 4 (DPC4), is a critical co-factor in signal transduction pathways activated by transforming growth factor (TGF)-beta-related ligands that regulate cell growth and differentiation. Mutations in Smad4/DPC4 have been identified in approximately 50% of pancreatic adenocarcinomas. Here we report that SCF(beta-TrCP1), a ubiquitin (E3) ligase, is a critical determinant for Smad4 protein degradation in pancreatic cancer cells. We found that F-box protein beta-TrCP1 in this E3 ligase interacted with Smad4 and that SCF(beta-TrCP1) inhibited TGF-beta biological activity in pancreatic cancer cells by decreasing Smad4 stability. Very low Smad4 protein levels in human pancreatic ductal adenocarcinoma cells were observed by immunohistochemistry. By analyzing pancreatic tumor-derived Smad4 mutants, we found that most point-mutated Smad4 proteins, except those within or very close to a mutation cluster region, exhibited higher interaction affinity with beta-TrCP1 and significantly elevated protein ubiquitination by SCF(beta-TrCP1). Furthermore, AsPC-1 and Caco-2, two cancer cell lines harboring Smad4 point mutations, exhibited rapid Smad4 protein degradation due to the effect of SCF(beta-TrCP1). Both Smad4 levels and TGF-beta signaling were elevated by retrovirus-delivered beta-TrCP1 siRNA in pancreatic cancer cells. Therefore, inhibition of Smad4-specific E3 ligase might be a target for therapeutic intervention in pancreatic cancer.