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Link to original content: https://pubmed.ncbi.nlm.nih.gov/33753508
Activated nanoscale actin-binding domain motion in the catenin-cadherin complex revealed by neutron spin echo spectroscopy - PubMed Skip to main page content
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. 2021 Mar 30;118(13):e2025012118.
doi: 10.1073/pnas.2025012118.

Activated nanoscale actin-binding domain motion in the catenin-cadherin complex revealed by neutron spin echo spectroscopy

Bela Farago  1 , Iain D Nicholl  2 , Shen Wang  3   4 , Xiaolin Cheng  5   4 , David J E Callaway  6 , Zimei Bu  6   7
Affiliations

Activated nanoscale actin-binding domain motion in the catenin-cadherin complex revealed by neutron spin echo spectroscopy

Bela Farago et al. Proc Natl Acad Sci U S A. .

Abstract

As the core component of the adherens junction in cell-cell adhesion, the cadherin-catenin complex transduces mechanical tension between neighboring cells. Structural studies have shown that the cadherin-catenin complex exists as an ensemble of flexible conformations, with the actin-binding domain (ABD) of α-catenin adopting a variety of configurations. Here, we have determined the nanoscale protein domain dynamics of the cadherin-catenin complex using neutron spin echo spectroscopy (NSE), selective deuteration, and theoretical physics analyses. NSE reveals that, in the cadherin-catenin complex, the motion of the entire ABD becomes activated on nanosecond to submicrosecond timescales. By contrast, in the α-catenin homodimer, only the smaller disordered C-terminal tail of ABD is moving. Molecular dynamics (MD) simulations also show increased mobility of ABD in the cadherin-catenin complex, compared to the α-catenin homodimer. Biased MD simulations further reveal that the applied external forces promote the transition of ABD in the cadherin-catenin complex from an ensemble of diverse conformational states to specific states that resemble the actin-bound structure. The activated motion and an ensemble of flexible configurations of the mechanosensory ABD suggest the formation of an entropic trap in the cadherin-catenin complex, serving as negative allosteric regulation that impedes the complex from binding to actin under zero force. Mechanical tension facilitates the reduction in dynamics and narrows the conformational ensemble of ABD to specific configurations that are well suited to bind F-actin. Our results provide a protein dynamics and entropic explanation for the observed force-sensitive binding behavior of a mechanosensitive protein complex.

Keywords: catch bond; cell adhesion; mechanotransduction; neutron spin echo spectroscopy; protein dynamics.

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Conflict of interest statement

The authors declare no competing interest.

Figures

Fig. 1.
Fig. 1.
Structure and domain organizations of the ABE complex. (A) The model shown represents an ensemble-averaged structure obtained from small-angle X-ray and neutron scattering experiments (36). (B) Domain organizations and function of α-catenin, β-catenin, and E-cadherin cytoplasmic tail that form the ABE complex.
Fig. 2.
Fig. 2.
NSE data on hydrogenated and selectively deuterated ABE complex in D2O buffer. (A–C) Representative I(q,t)/I(q, 0) functions of the fully hydrogenated hAhBhE complex (A), of hydrogenated α-catenin in complex with deuterated β-catenin and deuterated E-cadherin cytoplasmic tail hAdBdE (B), and deuterated α-catenin in complex with hydrogenated β-catenin and deuterated E-cadherin cytoplasmic tail dAhBdE (C). (D–F) Experimental Deff(q) of hAhBhE (black squares) (D), hAdBdE (red squares) (E), and dAhBdE (blue squares) (F) from the initial slope fittings of I(q,t)/I(q,0) data. Black line is the calculated Deff(q) curve assuming the whole ABE moves as a single rigid body (model 1 in Fig. 3). Red line is model 6 that best fits the experimental data. Other colored lines are the different models depicted in Fig. 3. Note that the effective diffusion constant Deff(Q = 0) should be the same as the diffusion constant Do measured by DLS only for the fully hydrogenated complex, but this is not true for the selectively deuterated complexes (82).
Fig. 3.
Fig. 3.
Models of moving segments within the ABE complex. Number of colors indicates the number of separately moving segments within the ABE complex. Model 6 shows the best agreement between theoretical calculations with NSE experimental data. See Fig. 1B for domain organization of α-catenin and β-catenin. Parsing α-catenin and β-catenin as separate moving segments results in Deff(q) that is significantly higher than the experimental data. SI Appendix, Fig. S6 shows that both the magnitude and q dependence of the calculated Deff(q) are sensitive to where the moving ABD domain is parsed in the linker region between M and ABD.
Fig. 4.
Fig. 4.
MD simulation analyses of ABE and α-catenin dimer. (A) Comparison of RMSFs of M domain and ABD for ABE and α-catenin dimer during the simulations (from 150 to 250 ns). Error bars are SDs over different trajectories. (B) Space visited by M domain and ABD during the 250-ns simulations. ABE is in marine, and α-catenin dimer is in magenta. (C) Conformational landscape of ABD projected along the first two PC modes sampled in the simulations. Green star denotes the position of the actin filament-bound conformation. (D) Contact map of M domain and ABD. Dark blue indicates contacts shared by both ABE and α-catenin dimer. Red contacts exist only in ABE while light blue shows contacts only in α-catenin dimer.
Fig. 5.
Fig. 5.
Biased MD simulation analyses of ABE under force. (A) Illustration of how external forces are applied in the simulations. (B) rmsd probability distributions of ABD during the pulling simulations of ABE and the unbiased simulations of ABE and α-catenin dimer. rmsd is calculated using the actin filament-bound structure as the reference. (C) Conformational landscape of ABD projected along the first two PC modes sampled in the pulling simulations. Green star denotes the position of the actin filament-bound conformation. (D) Two representative ABD structures from the left cluster (red) and the right cluster (blue), respectively, are shown.
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