Hanquier Jocelyne, Gimeno Thomas, Jeffers Victoria, Sullivan William J
Department of Microbiology & Immunology, Indiana University School of Medicine, Indianapolis, IN, USA.
Department of Pharmacology & Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.
Exp Parasitol. 2020 Feb 28;211:107868. doi: 10.1016/j.exppara.2020.107868.
Toxoplasma gondii is a protozoan parasite of great importance in human and veterinary health. The frontline treatment of antifolates suffers a variety of drawbacks, including toxicity and allergic reactions, underscoring the need to identify novel drug targets for new therapeutics to be developed. We previously showed that the Toxoplasma lysine acetyltransferase (KAT) GCN5b is an essential chromatin remodeling enzyme in the parasite linked to the regulation of gene expression. We have previously established that the KAT domain is a liability that can be targeted in the parasite by compounds like garcinol; here, we investigate the potential of the bromodomain as a targetable element of GCN5b. Bromodomains bind acetylated lysine residues on histones, which helps stabilize the KAT complex at gene promoters. Using an inducible dominant-negative strategy, we found that the GCN5b bromodomain is critical for Toxoplasma viability. We also found that the GCN5-family bromodomain inhibitor, L-Moses, interferes with the ability of the GCN5b bromodomain to associate with acetylated histone residues using an in vitro binding assay. Moreover, L-Moses displays potent activity against Toxoplasma tachyzoites in vitro, which can be overcome if parasites are engineered to over-express GCN5b. Collectively, our data support the GCN5b bromodomain as an attractive target for the development of new therapeutics.
刚地弓形虫是一种在人类和兽医健康领域具有重要意义的原生动物寄生虫。抗叶酸药物的一线治疗存在多种缺点，包括毒性和过敏反应，这突出表明需要确定新的药物靶点以开发新的治疗方法。我们之前表明，弓形虫赖氨酸乙酰转移酶（KAT）GCN5b是该寄生虫中一种与基因表达调控相关的必需染色质重塑酶。我们之前已经确定KAT结构域是一个易受攻击的部位，藤黄酚等化合物可以在该寄生虫中靶向作用于此结构域；在此，我们研究溴结构域作为GCN5b的一个可靶向元件的潜力。溴结构域结合组蛋白上的乙酰化赖氨酸残基，这有助于在基因启动子处稳定KAT复合物。使用诱导性显性负性策略，我们发现GCN5b溴结构域对弓形虫的生存能力至关重要。我们还发现，GCN5家族溴结构域抑制剂L-Moses在体外结合试验中会干扰GCN5b溴结构域与乙酰化组蛋白残基结合的能力。此外，L-Moses在体外对弓形虫速殖子显示出强大的活性，如果对寄生虫进行工程改造使其过表达GCN5b，这种活性可以被克服。总体而言，我们的数据支持将GCN5b溴结构域作为开发新治疗方法的一个有吸引力的靶点。
