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Structural basis for regulation of Arp2/3 complex by GMF

Nature Structural & Molecular Biology volume 20, pages 1062–1068 (2013)Cite this article

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Abstract

The Arp2/3 complex mediates formation of complex cellular structures such as lamellipodia by nucleating branched actin filaments. Arp2/3-complex activity is precisely controlled by over a dozen regulators, yet the structural mechanism by which regulators interact with the complex is unknown. GMF is a recently discovered regulator of the Arp2/3 complex that can inhibit nucleation and disassemble branches. We solved the structure of the 240-kDa assembly of Mus musculus GMF and Bos taurus Arp2/3 complex and found that GMF binds the barbed end of Arp2, overlapping with the proposed binding site of WASP-family proteins. The structure suggests that GMF can bind branch junctions in the manner that cofilin binds filament sides, consistent with a modified cofilin-like mechanism for debranching by GMF. The GMF-Arp2 interface reveals how the ADF-H actin-binding domain in GMF is exploited to specifically recognize Arp2/3 complex and not actin.

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Figure 1: Ribbon diagram of Bos taurus Arp2/3 complex with bound Mus musculus GMFγ, ATP and calcium.
Figure 2: Interaction of GMF with the barbed end of Arp2.
Figure 3: Interaction of GMF with the ARPC1 subunit.
Figure 4: Binding of GMF causes ordering of subdomains 1 and 2 of Arp2.
Figure 5: Structural basis for the specificity of GMF for Arp2 over actin or Arp3.
Figure 6: GMF may block binding of C to the barbed end of Arp2.
Figure 7: Model of GMF bound to a branch junction.

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Acknowledgements

Results shown in this report are derived from work performed at Argonne National Laboratory, Structural Biology Center at the Advanced Photon Source, beamline 19ID. Argonne is operated by University of Chicago Argonne, LLC, for the US Department of Energy, Office of Biological and Environmental Research under contract DE-AC02-06CH11357. We thank S. Ginell, J. Lazarz, B. Nocek and Y. Kim for assistance with remote data collection. We thank B. Goode (Brandeis University, Waltham, Massachusetts, USA) for sending mouse GMFγ expression plasmids and for discussing unpublished observations, and K. Needham for help with cloning and protein purification. We would also like to acknowledge K. Prehoda for comments on the manuscript. This work was financially supported by a US National Institutes of Health grant GM092917 (to B.J.N.) and the Pew Scholars in the Biomedical Sciences program.

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Authors and Affiliations

  1. Institute of Molecular Biology, University of Oregon, Eugene, Oregon, USA

    Qing Luan & Brad J Nolen

  2. Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon, USA

    Qing Luan & Brad J Nolen

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Q.L. and B.J.N. designed the research; Q.L. performed all experiments; Q.L. and B.J.N. analyzed the data and wrote the paper.

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Correspondence to Brad J Nolen.

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Luan, Q., Nolen, B. Structural basis for regulation of Arp2/3 complex by GMF. Nat Struct Mol Biol 20, 1062–1068 (2013). https://doi.org/10.1038/nsmb.2628

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