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Unambiguous Identification of β‐Tubulin as the Direct Cellular Target Responsible for the Cytotoxicity of Chalcone by Photoaffinity Labeling
Author(s) -
Zhou Bo,
Yu Xingxin,
Zhuang Chunlin,
Villalta Peter,
Lin Yong,
Lu Junxuan,
Xing Chengguo
Publication year - 2016
Publication title -
chemmedchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.817
H-Index - 100
eISSN - 1860-7187
pISSN - 1860-7179
DOI - 10.1002/cmdc.201600150
Subject(s) - chalcone , cytotoxicity , tubulin , cytotoxic t cell , peptide , chemistry , biochemistry , stereochemistry , in vitro , biology , microbiology and biotechnology , microtubule
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; IC 50 : 0.38±0.01 μ m ), 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.