Abstract
Actin binding compounds are widely used tools in cell biology. We compare the biological and biochemical effects of miuraenamide A and jasplakinolide, a structurally related prototypic actin stabilizer. Though both compounds have similar effects on cytoskeletal morphology and proliferation, they affect migration and transcription in a distinctive manner, as shown by a transcriptome approach in endothelial cells. In vitro, miuraenamide A acts as an actin nucleating, F-actin polymerizing and stabilizing compound, just like described for jasplakinolide. However, in contrast to jasplakinolide, miuraenamide A competes with cofilin, but not gelsolin or Arp2/3 for binding to F-actin. We propose a binding mode of miuraenamide A, explaining both its similarities and its differences to jasplakinolide. Molecular dynamics simulations suggest that the bromophenol group of miurenamide A interacts with residues Tyr133, Tyr143, and Phe352 of actin. This shifts the D-loop of the neighboring actin, creating tighter packing of the monomers, and occluding the binding site of cofilin. Since relatively small changes in the molecular structure give rise to this selectivity, actin binding compounds surprisingly are promising scaffolds for creating actin binders with specific functionality instead of just “stabilizers”.
Highlights
Actin binding compounds are widely used tools in cell biology
We investigated whether of miuraenamide A (MiuA) affects the binding of actin binding proteins (ABPs) to G-actin
MiuA did not affect Arp2/3 complex binding to F-actin, since the amounts of Arp2/3 complex in F-actin pellet were similar in the presence or absence of MiuA (Fig. 3c). These results suggest that MiuA selectively interferes with the binding of cofilin to F-actin, and that this action is specific for MiuA, since it was not mimicked by jasplakinolide
Summary
We compare the biological and biochemical effects of miuraenamide A and jasplakinolide, a structurally related prototypic actin stabilizer Though both compounds have similar effects on cytoskeletal morphology and proliferation, they affect migration and transcription in a distinctive manner, as shown by a transcriptome approach in endothelial cells. Actin binding proteins continuously compete with each other for binding sites on actin (e.g. thymosin beta[4] with profilin[6], or MRTF with G-actin7) and with actin itself 5 This complex network allows for subtle control of the “actin-interactome” and related cell functions. Kabiramide C has been shown to compete with actin capping proteins like gelsolin in a kind of “molecular mimicry”[8] This aspect of the interaction between small molecular inhibitors and actin has been largely neglected during their discovery and characterization. In the context of protein-protein interactions and transcriptional regulation MiuA shows striking functional differences to jasplakinolide, which can be in part explained by the unique binding mode we suggest
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