School of Basic Sciences, Indian Institute of Technology Bhubaneswar, India.
FEBS J. 2022 Feb;289(3):832-853. doi: 10.1111/febs.16212. Epub 2021 Oct 10.
Mycobacterium leprae, the causative organism of leprosy, harbors many antigenic proteins, and one such protein is the 18-kDa antigen. This protein belongs to the small heat shock protein family and is commonly known as HSP18. Its chaperone function plays an important role in the growth and survival of M. leprae inside infected hosts. HSP18/18-kDa antigen is often used as a diagnostic marker for determining the efficacy of multidrug therapy (MDT) in leprosy. However, whether MDT drugs (dapsone, clofazimine, and rifampicin) do interact with HSP18 and how these interactions affect its structure and chaperone function is still unclear. Here, we report evidence of HSP18-dapsone/clofazimine/rifampicin interaction and its impact on the structure and chaperone function of HSP18. These three drugs interact efficiently with HSP18 (having submicromolar binding affinity) with 1 : 1 stoichiometry. Binding of these MDT drugs to the 'α-crystallin domain' of HSP18 alters its secondary structure and tryptophan micro-environment. Furthermore, surface hydrophobicity, oligomeric size, and thermostability of the protein are reduced upon interaction with these three drugs. Eventually, all these structural alterations synergistically decrease the chaperone function of HSP18. Interestingly, the effect of rifampicin on the structure, stability, and chaperone function of this mycobacterial small heat shock protein is more pronounced than the other two MDT drugs. This reduction in the chaperone function of HSP18 may additionally abate M. leprae survivability during multidrug treatment. Altogether, this study provides a possible foundation for rational designing and development of suitable HSP18 inhibitors in the context of effective treatment of leprosy.
麻风分枝杆菌是麻风病的病原体，它含有许多抗原蛋白，其中一种蛋白是 18kDa 抗原。这种蛋白属于小热休克蛋白家族，通常被称为 HSP18。它的伴侣功能在麻风分枝杆菌在感染宿主内的生长和存活中起着重要作用。HSP18/18kDa 抗原通常被用作确定麻风病多药治疗（MDT）疗效的诊断标志物。然而，MDT 药物（氨苯砜、氯法齐明和利福平）是否与 HSP18 相互作用，以及这些相互作用如何影响其结构和伴侣功能仍不清楚。在这里，我们报告了 HSP18-氨苯砜/氯法齐明/利福平相互作用的证据及其对 HSP18 结构和伴侣功能的影响。这三种药物与 HSP18 有效相互作用（具有亚微摩尔结合亲和力），具有 1：1 的化学计量比。这些 MDT 药物与 HSP18 的“α-晶体结构域”结合会改变其二级结构和色氨酸微环境。此外，与这三种药物相互作用会降低蛋白质的表面疏水性、寡聚体大小和热稳定性。最终，所有这些结构改变协同降低 HSP18 的伴侣功能。有趣的是，利福平对这种细菌小热休克蛋白的结构、稳定性和伴侣功能的影响比其他两种 MDT 药物更为明显。这种 HSP18 伴侣功能的降低可能会进一步减少麻风分枝杆菌在多药治疗期间的存活能力。总的来说，这项研究为在有效治疗麻风病的背景下合理设计和开发合适的 HSP18 抑制剂提供了一个可能的基础。
