Unambiguous Identification of β-Tubulin as the Direct Cellular Target Responsible for the Cytotoxicity of Chalcone by Photoaffinity Labeling

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• 作者：Dr. Bo Zhou ; Prof. Xingxin Yu ; Dr. Chunlin Zhuang ; Dr. Peter Villalta ; Prof. Yong Lin ; Prof. Junxuan Lu and Prof. Chengguo Xing
• 刊名：ChemMedChem
• 出版年：2016
• 出版时间：July 5, 2016
• 年：2016
• 卷：11
• 期：13
• 页码：1436-1445
• 全文大小：1260K
• ISSN：1860-7187

文摘

Chalcone is a simple and potentially privileged structure in medicinal chemistry with a diverse repertoire of biological activities, among which cytotoxicity is of particular interest. The sharp structure–activity relationship (SAR) for chalcone's cytotoxicity suggests structure-specific target interactions. Despite the numerous putative targets proposed, evidence for direct target interactions in cells is unavailable. In this study, guided by the sharp cytotoxic SAR, we developed a cytotoxic chalcone-based photoaffinity labeling (PAL) probe, (E)-3-(3-azidophenyl)-1-[3,5-dimethoxy-4-(prop-2-yn-1-yloxy)phenyl]-2-methylprop-2-en-1-one (C95; IC₅₀: 0.38±0.01 μm), along with two structurally similar non-cytotoxic probes. These probes were used to search for the direct cellular target responsible for chalcone's cytotoxicity through intact cell-based PAL experiments, in which β-tubulin was identified to specifically interact with the cytotoxic probe (i.e., C95) but not the non-cytotoxic probes. A set of phenotypical and biochemical assays further reinforced β-tubulin as the cytotoxic target of chalcones. Peptide mass quantitation by mass spectrometric analysis revealed one peptide potentially labeled by C95, providing information on chalcone's binding site on β-tubulin.