The pursuit of novel therapeutics is a complex and resource-intensive endeavor marked by significant challenges, including high costs and low success rates. In response, drug repositioning strategies leverage existing FDA-approved compounds to predict their efficacy across diverse diseases. Peptidyl arginine deiminase 4 (PAD4) plays a pivotal role in protein citrullination, a process implicated in the autoimmune pathogenesis of rheumatoid arthritis (RA). Targeting PAD4 has thus emerged as a promising therapeutic approach. This study employs computational and enzyme inhibition strategies to identify potential PAD4-targeting compounds from a library of FDA-approved drugs. In silico docking analyses validated the binding interactions and orientations of screened compounds within PAD4's active site, with key residues such as ASP350, HIS471, ASP473, and CYS645 participating in crucial hydrogen bonding and van der Waals interactions. Molecular dynamics simulations further assessed the stability of top compounds exhibiting high binding affinities. Among these compounds, Saquinavir (SQV) emerged as a potent PAD4 inhibitor, demonstrating competitive inhibition with a low IC50 value of 1.21 ± 0.04 µM. In vitro assays, including enzyme kinetics and biophysical analyses, highlighted significant changes in PAD4 conformation upon SQV binding, as confirmed by circular dichroism spectroscopy. SQV induced localized alterations in PAD4 structure, effectively occupying the catalytic pocket and inhibiting enzymatic activity. These findings underscore SQV's potential as a therapeutic candidate for RA through PAD4 inhibition. Further validation through in vitro and in vivo studies is essential to confirm SQV's therapeutic benefits in autoimmune diseases associated with dysregulated citrullination.

中文翻译：

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批准药物的改进作用：沙奎那韦肽基精氨酸脱亚胺酶 4 抑制类风湿关节炎的综合计算和生物物理分析。


寻求新疗法是一项复杂且资源密集型的工作，面临着巨大的挑战，包括高成本和低成功率。作为回应，药物重新定位策略利用 FDA 批准的现有化合物来预测其在不同疾病中的疗效。肽基精氨酸脱亚胺酶 4 (PAD4) 在蛋白质瓜氨酸化中发挥关键作用，这一过程与类风湿性关节炎 (RA) 的自身免疫发病机制有关。因此，靶向 PAD4 已成为一种有前途的治疗方法。本研究采用计算和酶抑制策略从 FDA 批准的药物库中识别潜在的 PAD4 靶向化合物。计算机对接分析验证了 PAD4 活性位点内筛选化合物的结合相互作用和方向，其中 ASP350、HIS471、ASP473 和 CYS645 等关键残基参与关键的氢键和范德华相互作用。分子动力学模拟进一步评估了表现出高结合亲和力的顶级化合物的稳定性。在这些化合物中，沙奎那韦 (SQV) 成为一种有效的 PAD4 抑制剂，表现出竞争性抑制作用，IC50 值低至 1.21 ± 0.04 µM。包括酶动力学和生物物理分析在内的体外测定强调了 SQV 结合后 PAD4 构象的显着变化，如圆二色光谱所证实。 SQV 诱导 PAD4 结构的局部改变，有效地占据催化口袋并抑制酶活性。这些发现强调了 SQV 通过抑制 PAD4 作为 RA 治疗候选药物的潜力。 通过体外和体内研究的进一步验证对于确认 SQV 在与瓜氨酸失调相关的自身免疫性疾病中的治疗效果至关重要。