The dual mode of action of bistramide A entails severing of filamentous actin and covalent protein modification

doi:10.1073/pnas.0710727105

The dual mode of action of bistramide A entails severing of filamentous actin and covalent protein modification

Departments of *Chemistry and
^†Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637

Edited by Robert Haselkorn, University of Chicago, Chicago, IL, and approved January 10, 2008 (received for review November 12, 2007)

Abstract

This study provides comprehensive characterization of the mode of action of bistramide A and identifies structural requirements of bistramide-based compounds that are responsible for severing actin filaments and inhibiting growth of cancer cells in vitro and in vivo. We rationally designed and assembled a series of structural analogs of the natural product, including a fluorescently labeled conjugate. We used TIRF microscopy to directly observe actin filament severing by this series of small molecules, which established that the combination of the spiroketal and the amide subunits was sufficient to enable rapid actin filament disassembly in vitro. In addition, we demonstrated that the enone subunit of bistramide A is responsible for covalent modification of the protein in vitro and in A549 cells, resulting in further increase in the cytotoxicity of the natural product. Our results demonstrate that bistramide A elicits its potent antiproliferative activity by a dual mechanism of action, which entails both severing of actin filaments and covalent sequestration of monomeric actin in the cell.

Footnotes

^‡To whom correspondence should be addressed. E-mail: skozmin{at}uchicago.edu
Author contributions: R.S.R. and S.A.K. designed research; and S.A.R., D.S.C., and V.A.K. performed research.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0710727105/DC1.