1] Division of Immunology, Allergy and Infectious Diseases, Department of Dermatology, Medical University of Vienna, Vienna, Austria [2] CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria.
CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria.
Oncogene. 2014 May 8;33(19):2531-9. doi: 10.1038/onc.2013.185. Epub 2013 Jun 3.
The microphthalmia-associated transcription factor (MITF) is indispensable for the viability of melanocytic cells, is an oncogene in melanoma and has a cell type-specific expression pattern. As the modulation of MITF activity by direct chemical targeting remains a challenge, we assessed a panel of drugs for their ability to downregulate MITF expression or activity by targeting its upstream modulators. We found that the multi-kinase inhibitors midostaurin and sunitinib downregulate MITF protein levels. To identify the target molecules shared by both the drugs in melanocytic cells, a chemical proteomic approach was applied and AMP-activated kinase (AMPK) was identified as the relevant target for the observed phenotype. RNA interference and chemical inhibition of AMPK led to a decrease in MITF protein levels. Reduction of MITF protein levels was the result of proteasomal degradation, which was preceded by enhanced phosphorylation of MITF mediated by ERK. As expected, downregulation of MITF protein levels by AMPK inhibition was associated with decreased viability. Together, these results identify AMPK as an important regulator for the maintenance of MITF protein levels in melanocytic cells.
小眼畸形相关转录因子（MITF）对于黑素细胞的存活是必不可少的，它是黑色素瘤中的癌基因，并且具有细胞类型特异性的表达模式。由于直接化学靶向MITF 活性的调节仍然是一个挑战，我们评估了一组药物通过靶向其上游调节剂来下调 MITF 表达或活性的能力。我们发现多激酶抑制剂米哚妥林和舒尼替尼下调 MITF 蛋白水平。为了鉴定两种药物在黑素细胞中共同作用的靶分子，应用了化学蛋白质组学方法，发现 AMP 激活的蛋白激酶 (AMPK) 是观察到的表型的相关靶标。RNA 干扰和 AMPK 的化学抑制导致 MITF 蛋白水平降低。MITF 蛋白水平的降低是由于蛋白酶体降解，这是由 ERK 介导的 MITF 增强磷酸化所引发的。正如预期的那样，AMPK 抑制下调 MITF 蛋白水平与活力降低有关。总之，这些结果表明 AMPK 是维持黑素细胞中 MITF 蛋白水平的重要调节剂。
