Department of Chemistry, University of Nebraska-Lincoln , Lincoln, Nebraska 68588, United States.
Biochemistry. 2014 Mar 4;53(8):1360-72. doi: 10.1021/bi401329a. Epub 2014 Feb 19.
Pancreatic cancer has a dismal 5 year survival rate of 5.5% that has not been improved over the past 25 years despite an enormous amount of effort. Thus, there is an urgent need to identify truly novel yet druggable protein targets for drug discovery. The human protein DnaJ homologue subfamily A member 1 (DNAJA1) was previously shown to be downregulated 5-fold in pancreatic cancer cells and has been targeted as a biomarker for pancreatic cancer, but little is known about the specific biological function for DNAJA1 or the other members of the DnaJ family encoded in the human genome. Our results suggest the overexpression of DNAJA1 suppresses the stress response capabilities of the oncogenic transcription factor, c-Jun, and results in the diminution of cell survival. DNAJA1 likely activates a DnaK protein by forming a complex that suppresses the JNK pathway, the hyperphosphorylation of c-Jun, and the anti-apoptosis state found in pancreatic cancer cells. A high-quality nuclear magnetic resonance solution structure of the J-domain of DNAJA1 combined with a bioinformatics analysis and a ligand affinity screen identifies a potential DnaK binding site, which is also predicted to overlap with an inhibitory binding site, suggesting DNAJA1 activity is highly regulated.
胰腺癌的 5 年生存率仅为 5.5%，尽管过去 25 年来投入了大量的努力，但这一数据并未得到改善。因此，迫切需要确定真正新颖且可成药的蛋白靶标用于药物发现。人类蛋白 DnaJ 同源物亚家族 A 成员 1（DNAJA1）先前已被证明在胰腺癌细胞中下调 5 倍，并且已被作为胰腺癌的生物标志物进行靶向治疗，但对于 DNAJA1 或人类基因组中编码的 DnaJ 家族的其他成员的具体生物学功能知之甚少。我们的研究结果表明，DNAJA1 的过表达可抑制致癌转录因子 c-Jun 的应激反应能力，并导致细胞存活减少。DNAJA1 可能通过形成复合物激活 DnaK 蛋白，从而抑制 JNK 通路、c-Jun 的过度磷酸化和胰腺癌细胞中的抗凋亡状态。DNAJA1 的 J 结构域的高质量核磁共振溶液结构结合生物信息学分析和配体亲和力筛选，确定了一个潜在的 DnaK 结合位点，该位点也预测与抑制性结合位点重叠，表明 DNAJA1 的活性受到高度调控。
