Petrilli Alejandra, Bott Marga, Fernández-Valle Cristina
Department of Biomedical Science, College of Medicine, University of Central Florida, Lake Nona-Orlando, Florida, USA.
Oncotarget. 2013 Dec;4(12):2354-65. doi: 10.18632/oncotarget.1422.
Mutations in the NF2 gene cause Neurofibromatosis Type 2 (NF2), a disorder characterized by the development of schwannomas, meningiomas and ependymomas in the nervous system. Merlin, a tumor suppressor encoded by the NF2 gene, modulates activity of many essential signaling pathways. Yet despite increasing knowledge of merlin function, there are no NF2 drug therapies. In a pilot high-throughput screen of the Library of Pharmacologically Active Compounds, we assayed for compounds capable of reducing viability of mouse Schwann cells (MSC) with Nf2 inactivation as a cellular model for human NF2 schwannomas. AGK2, a SIRT2 (sirtuin 2) inhibitor, was identified as a candidate compound. SIRT2 is one of seven mammalian sirtuins that are NAD+-dependent protein deacetylases. We show that merlin-mutant MSC have higher expression levels of SIRT2 and lower levels of overall lysine acetylation than wild-type control MSC. Pharmacological inhibition of SIRT2 decreases merlin-mutant MSC viability in a dose dependent manner without substantially reducing wild-type MSC viability. Inhibition of SIRT2 activity in merlin-mutant MSC is accompanied by release of lactate dehydrogenase and high mobility group box 1 protein into the medium in the absence of significant apoptosis, autophagy, or cell cycle arrest. These findings suggest that SIRT2 inhibition triggers necrosis of merlin-mutant MSCs and that SIRT2 is a potential NF2 drug target.
NF2基因的突变会导致2型神经纤维瘤病（NF2），该疾病的特征是在神经系统中形成神经鞘瘤、脑膜瘤和室管膜瘤。Merlin是由NF2基因编码的一种肿瘤抑制因子，可调节许多重要信号通路的活性。然而，尽管对merlin功能的了解不断增加，但目前尚无针对NF2的药物治疗方法。在一项对药理活性化合物库进行的高通量筛选试验中，我们以Nf2失活的小鼠雪旺细胞（MSC）作为人类NF2神经鞘瘤的细胞模型，检测了能够降低其活力的化合物。AGK2，一种SIRT2（沉默调节蛋白2）抑制剂，被鉴定为候选化合物。SIRT2是七种依赖NAD+的蛋白质脱乙酰酶的哺乳动物沉默调节蛋白之一。我们发现，与野生型对照MSC相比，merlin突变的MSC具有更高的SIRT2表达水平和更低的总体赖氨酸乙酰化水平。对SIRT2的药理抑制以剂量依赖的方式降低merlin突变的MSC活力，而不会显著降低野生型MSC的活力。在merlin突变的MSC中抑制SIRT2活性伴随着乳酸脱氢酶和高迁移率族蛋白B1释放到培养基中，且不存在明显的细胞凋亡、自噬或细胞周期停滞。这些发现表明，抑制SIRT2会触发merlin突变的MSC坏死，并且SIRT2是一个潜在的NF2药物靶点。
