McMahon J B, Currens M J, Gulakowski R J, Buckheit R W, Lackman-Smith C, Hallock Y F, Boyd M R
Laboratory of Drug Discovery Research and Development, National Cancer Institute, Frederick, Maryland 21702-1201, USA.
Antimicrob Agents Chemother. 1995 Feb;39(2):484-8. doi: 10.1128/AAC.39.2.484.
Studies of the mechanism of action of michellamine B, a novel anti-human immunodeficiency virus (HIV) alkaloid from the tropical plant Ancistrocladus korupensis, have revealed that the compound acts at two distinct stages of the HIV life cycle. The compound had no direct effect on HIV virions and did not block the initial binding of HIV to target cells. Postinfection time course studies revealed that the agent partially inhibited HIV-induced cell killing and syncytium formation when added up to 48 h following acute infection; however, viral reproduction was fully inhibited only when the compound was added immediately after infection. Time-limited treatments of HIV-infected cells revealed that michellamine B had to be present continuously to provide maximum antiviral protection. HIV replication in cells in which infection was already fully established or in chronically infected cells was unaffected by michellamine B. Biochemical studies showed that michellamine B inhibited the enzymatic activities of reverse transcriptases (RTs) from both HIV type 1 and HIV type 2 as well as two different nonnucleoside drug-resistant RTs with specific amino acid substitutions. In addition, human DNA polymerases alpha and beta were inhibited by the alkaloid. Michellamine B exerted a potent dose-dependent inhibition of cell fusion in two independent cell-based fusion assays. Thus, michellamine B acts both at an early stage of the HIV life cycle by inhibiting RT as well as at later stages by inhibiting cellular fusion and syncytium formation.
对米切拉明B作用机制的研究表明，这种从热带植物科鲁普钩枝藤中提取的新型抗人类免疫缺陷病毒（HIV）生物碱，在HIV生命周期的两个不同阶段发挥作用。该化合物对HIV病毒粒子没有直接影响，也不阻断HIV与靶细胞的初始结合。感染后时间进程研究表明，在急性感染后48小时内添加该药物，可部分抑制HIV诱导的细胞杀伤和多核体形成；然而，只有在感染后立即添加该化合物，病毒复制才会被完全抑制。对HIV感染细胞进行限时处理表明，米切拉明B必须持续存在才能提供最大程度的抗病毒保护。米切拉明B对已经完全建立感染的细胞或慢性感染细胞中的HIV复制没有影响。生化研究表明，米切拉明B抑制了1型和2型HIV逆转录酶（RT）以及两种具有特定氨基酸替代的不同非核苷类耐药RT的酶活性。此外，该生物碱还抑制了人类DNA聚合酶α和β。在两种基于细胞的独立融合试验中，米切拉明B对细胞融合表现出强大的剂量依赖性抑制作用。因此，米切拉明B通过抑制RT在HIV生命周期的早期发挥作用，并通过抑制细胞融合和多核体形成在后期发挥作用。
