Structural Basis of Arp2/3 Complex Inhibition by GMF, Coronin, and Arpin

• Published in: Journal of molecular biology 2017-01, Vol.429 (2), p.237-248
• Main Authors: Sokolova, Olga S., Chemeris, Angelina, Guo, Siyang, Alioto, Salvatore L., Gandhi, Meghal, Padrick, Shae, Pechnikova, Evgeniya, David, Violaine, Gautreau, Alexis, Goode, Bruce L.
• Format: Article
• Language: English
• Subjects: 4-Butyrolactone - analogs & derivatives; 4-Butyrolactone - pharmacology; actin nucleation; Actin-Related Protein 2-3 Complex - antagonists & inhibitors; Actin-Related Protein 2-3 Complex - chemistry; Binding Sites; Biochemistry, Molecular Biology; Cancer; Carrier Proteins - pharmacology; Cell Movement - drug effects; Cellular Biology; conformation; Endocytosis - drug effects; Glia Maturation Factor - pharmacology; Humans; Imaging, Three-Dimensional; Life Sciences; Molecular biology; Protein Conformation; Quantitative Methods; single-particle EM; yeast
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2016.11.030

The evolutionarily conserved Arp2/3 complex plays a central role in nucleating the branched actin filament arrays that drive cell migration, endocytosis, and other processes. To better understand Arp2/3 complex regulation, we used single-particle electron microscopy to compare the structures of Arp2/3 complex bound to three different inhibitory ligands: glia maturation factor (GMF), Coronin, and Arpin. Although the three inhibitors have distinct binding sites on Arp2/3 complex, they each induced an “open” nucleation-inactive conformation. Coronin promoted a standard (previously described) open conformation of Arp2/3 complex, with the N-terminal β-propeller domain of Coronin positioned near the p35/ARPC2 subunit of Arp2/3 complex. GMF induced two distinct open conformations of Arp2/3 complex, which correlated with the two suggested binding sites for GMF. Furthermore, GMF synergized with Coronin in inhibiting actin nucleation by Arp2/3 complex. Arpin, which uses VCA-related acidic (A) motifs to interact with the Arp2/3 complex, induced the standard open conformation, and two new masses appeared at positions near Arp2 and Arp3. Furthermore, Arpin showed additive inhibitory effects on Arp2/3 complex with Coronin and GMF. Together, these data suggest that Arp2/3 complex conformation is highly polymorphic and that its activities can be controlled combinatorially by different inhibitory ligands. [Display omitted] •Coronin, GMF, and Arpin each induce related open conformations in Arp2/3 complex.•GMF binding induces two distinct inhibitory states of Arp2/3 complex.•Coronin, GMF, and Arpin combinatorially inhibit Arp2/3 complex activity.•Arpin has two separate binding sites on Arp2/3 complex Arp2 and Arp3.