Pradhan Swagat, Mahaddalkar Tejashree, Choudhary Sinjan, Manhcukonda Naresh, Nagireddy Praveen Reddy, Kantevari Srinivas, Lopus Manu
Experimental Cancer Therapeutics and Chemical Biology, UM-DAE Centre for Excellence in Basic Sciences, Kalina, Mumbai, India.
Organic Chemistry Division-II (CPC Division), CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, Telangana, India.
Curr Top Med Chem. 2017;17(22):2569-2574. doi: 10.2174/1568026617666170104150304.
We have recently reported the synthesis and antiproliferative potential of a series of biaryl type α-noscapine congeners. Among them, 9-(3-pyridyl) noscapine 3f (9-PyNos, henceforth), which was synthesized by adding pyridine unit to the tetrahydroisoquinoline part of natural α-noscapine core, was found to be the most effective one to inhibit proliferation of a variety of cancer cell lines. However, details of its interactions with its cellular target, tubulin, remain poorly understood. In this report, we examined the nature of interactions of 9-PyNos with tubulin based on the methodologies of spectrofluorimetry, circular dichroism, and turbidimetry techniques. Far-UV circular dichroism spectra indicated perturbation of tubulin secondary structure in the presence of 9-PyNos, not amounting, however, to the perturbation induced by noscapine. The noscapinoid nevertheless altered the surface configuration of the protein considerably, as indicated by an anilinonaphthalene sulphonate binding assay, and promoted colchicine binding to tubulin, the latter indicating its adjacent binding site with colchicine. 9-PyNos however, did not alter microtubule assembly considerably. Investigating the possible reason behind this apparent lack of strong inhibition of microtubule assembly, we found that the binding interactions of tubulin with 9-PyNos do not involve modification of cysteine residues of tubulin. Taken together, our data suggest that the antiproliferative mechanism of action of 9-PyNos involves disruption of structural integrity of tubulin without strong inhibition of tubulin assembly.
我们最近报道了一系列联芳基型α-那可丁类似物的合成及其抗增殖潜力。其中，9-(3-吡啶基)那可丁3f（以下简称9-PyNos）是通过在天然α-那可丁核心的四氢异喹啉部分添加吡啶单元合成的，被发现是抑制多种癌细胞系增殖最有效的一种。然而，其与细胞靶点微管蛋白相互作用的细节仍知之甚少。在本报告中，我们基于荧光光谱法、圆二色性和比浊法技术研究了9-PyNos与微管蛋白相互作用的性质。远紫外圆二色光谱表明，在9-PyNos存在下微管蛋白二级结构受到扰动，但程度不及那可丁引起的扰动。然而，如苯胺萘磺酸盐结合试验所示，那可丁类化合物显著改变了蛋白质的表面构型，并促进秋水仙碱与微管蛋白结合，后者表明其与秋水仙碱的相邻结合位点。然而，9-PyNos并没有显著改变微管组装。在研究这种明显缺乏对微管组装强烈抑制作用背后的可能原因时，我们发现微管蛋白与9-PyNos的结合相互作用不涉及微管蛋白半胱氨酸残基的修饰。综上所述，我们的数据表明，9-PyNos的抗增殖作用机制涉及破坏微管蛋白的结构完整性，而不强烈抑制微管蛋白组装。
