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. 2018 Aug 21;115(4):642-654.
doi: 10.1016/j.bpj.2018.07.005. Epub 2018 Jul 11.

α-Catenin Structure and Nanoscale Dynamics in Solution and in Complex with F-Actin

Iain D Nicholl  1 , Tsutomu Matsui  2 , Thomas M Weiss  2 , Christopher B Stanley  3 , William T Heller  3 , Anne Martel  4 , Bela Farago  4 , David J E Callaway  5 , Zimei Bu  6
Affiliations

α-Catenin Structure and Nanoscale Dynamics in Solution and in Complex with F-Actin

Iain D Nicholl et al. Biophys J. .

Abstract

As a core component of the adherens junction, α-catenin stabilizes the cadherin/catenin complexes to the actin cytoskeleton for the mechanical coupling of cell-cell adhesion. α-catenin also modulates actin dynamics, cell polarity, and cell-migration functions that are independent of the adherens junction. We have determined the solution structures of the α-catenin monomer and dimer using in-line size-exclusion chromatography small-angle X-ray scattering, as well as the structure of α-catenin dimer in complex to F-actin filament using selective deuteration and contrast-matching small angle neutron scattering. We further present the first observation, to our knowledge, of the nanoscale dynamics of α-catenin by neutron spin-echo spectroscopy, which explicitly reveals the mobile regions of α-catenin that are crucial for binding to F-actin. In solution, the α-catenin monomer is more expanded than either protomer shown in the crystal structure dimer, with the vinculin-binding M fragment and the actin-binding domain being able to adopt different configurations. The α-catenin dimer in solution is also significantly more expanded than the dimer crystal structure, with fewer interdomain and intersubunit contacts than the crystal structure. When in complex to F-actin, the α-catenin dimer has an even more open and extended conformation than in solution, with the actin-binding domain further separated from the main body of the dimer. The α-catenin-assembled F-actin bundle develops into an ordered filament packing arrangement at increasing α-catenin/F-actin molar ratios. Together, the structural and dynamic studies reveal that α-catenin possesses dynamic molecular conformations that prime this protein to function as a mechanosensor protein.

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Figures

Figure 1
Figure 1
α-Catenin and SEC-SAXS analysis. (A) The primary structure and domains in α-catenin are shown. (B) SEC-ultraviolet of α-catenin is shown. The fractions at elution volume 10.9 and 12.5 mL correspond to dimeric and monomeric α-catenin, respectively. (C) SEC-SAXS of the dimer and monomer peaks is shown. (D) SEC-SAXS of the dimer peak is shown. (E) SEC-SAXS of the monomer peak is shown. Note that because (E) used a different SEC column from (C) and (D), the peak positions are shifted. The arrows in (D) and (E) mark the fractions of SAXS data selected for further analysis as shown in Fig. 2.
Figure 2
Figure 2
(A) SEC-SAXS of the dimer (filled black dots) and monomer fractions (open black circles). (B) The P(r) functions of dimer (filled black dots) and monomer (open black circles) calculated from SAXS data are shown. (C) A comparison of the P(r) of the SEC-SAXS monomer fraction (open black circles) with that calculated from crystal structure (one of the PDB: 4IGG protomers) after the disordered regions were reconstructed (black line). (D) A comparison of the P(r) of the SEC-SAXS dimer fraction (filled black dots) with that calculated from crystal structure (PDB: 4IGG) after the disordered regions were reconstructed in the PDB file (black line).
Figure 3
Figure 3
Solution structures of α-catenin monomer. (A) A SAXS curve computed from structural models generated from SASSIE Monte Carlo simulation (green and blue lines) with best fit to the monomer fraction of experimental SEC-SAXS data (black square) is shown, χ2 < 0.98. (B) A χ2 vs. Rg plot of the fits of SASSIE generated models to the monomer SEC-SAXS data is shown. (C) Two representative structural models of open and closed α-catenin monomer with minimized χ2 fit to the experimental SAXS data are shown.
Figure 4
Figure 4
Solution structure of α-catenin dimer. (A) A SAXS curve of an α-catenin dimer model generated from SASSIE Monte Carlo simulation (red line) with best fit to the dimer fraction of SEC-SAXS data (black square) is shown, χ2 < 1.21. (B) χ2 vs. Rg plots of the fits of SASSIE generated models to the dimer SEC-SAXS data are shown. Two rounds of simulations are performed to minimize the χ2. (C) A representative α-catenin dimer structural model with minimized χ2 is shown.
Figure 5
Figure 5
Structure of dα-catenin dimer in complex to F-actin in 40% D2O at the contrast matching point of F-actin. (A) SANS on the dα-catenin/F-actin complex in 40% D2O buffer at the matching point of F-actin (black square) is shown. The red line is the fit of the structural model shown in (D). The concentration of dα-catenin is 1.74 mg/mL. The concentration of actin is ∼5 mg/mL. The actin/dα-catenin molar ratio is 6.8:1. (B) The P(r) of dα-catenin/F-actin complex in 40% D2O that corresponds to the conformational of dα-catenin (filled black square) is shown, as compared to that of α-catenin dimer in solution from SEC-SAXS (open black square). (C) A χ2 vs. Rg plot of the fit of SASSIE Monte Carlo generated structures to the SANS data in 40% D2O buffer is shown. (D) A representative structural model of dα-catenin with a best fit to the experimental SANS data is shown, χ2 < 0.9.
Figure 6
Figure 6
(A) Contrast-matched SANS on the dα-catenin/F-actin complex in 100% D2O buffer at the matching point of dα-catenin. The three panels are the I(Q) of the complex at different actin/dα-catenin molar ratios, with a distinct correlation peak appearing at molar ratio = 3.8 (see arrow). The actin concentration is kept at 81.5 μM in all three panels. (B) The structure factor S(Q) of the F-actin bundle, generated by normalizing the I(Q) at molar ratio = 3.8 (bottom panel) by the I(Q) at molar ratio = 15.1 (top panel), is shown. (C) The left panel shows a negative-staining electron microscopy image of F-actin filament mixed with ezrin, a protein that does not bundle F-actin. The right panel shows a negative-staining electron microscopy image of an α-catenin-assembled F-actin bundle. (D) A structural model of the dα-catenin dimer between two actin filaments is shown.
Figure 7
Figure 7
NSE spectroscopy of α-catenin dimer. (A), (B) and (C) show intermediate correlation function I(Q,t)/I(Q,0) as a function of Fourier time at different Q values. The lines are single exponential fits to the initial slope of I(Q,t)/I(Q,0). Note that at Q between 0.0509–0.1379 Å−1I(Q,t)/I(Q,0), shows non-single exponential behavior. (D) The effective diffusion constants Deff(Q) (black squares) obtained from the initial slopes of the spectra in (A), (B) and (C) are shown. The solid red line is the theoretical Deff(Q) using the coordinates of α-catenin dimer shown in Fig. 4C, assuming the α -catenin dimer is a rigid body. The dashed red line is the theoretical Deff(Q), assuming amino acid residues 836–906 in each protomer of the dimer are moving. (E) The dynamics of α-Catenin dimer colored by normal mode analysis, with blue representing low mobility and red high mobility, is shown.
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References

    1. Kobielak A., Fuchs E. Alpha-catenin: at the junction of intercellular adhesion and actin dynamics. Nat. Rev. Mol. Cell Biol. 2004;5:614–625. - PMC - PubMed
    1. Gumbiner B.M. Cell adhesion: the molecular basis of tissue architecture and morphogenesis. Cell. 1996;84:345–357. - PubMed
    1. Takeichi M. Dynamic contacts: rearranging adherens junctions to drive epithelial remodelling. Nat. Rev. Mol. Cell Biol. 2014;15:397–410. - PubMed
    1. Brasch J., Harrison O.J., Shapiro L. Thinking outside the cell: how cadherins drive adhesion. Trends Cell Biol. 2012;22:299–310. - PMC - PubMed
    1. Drees F., Pokutta S., Weis W.I. Alpha-catenin is a molecular switch that binds E-cadherin-beta-catenin and regulates actin-filament assembly. Cell. 2005;123:903–915. - PMC - PubMed

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